/[pub]/test/html-webhacc/error-description-source.xml
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revision 1.1 by wakaba, Sun Jul 1 10:02:24 2007 UTC revision 1.22 by wakaba, Sat Apr 12 15:57:56 2008 UTC
# Line 11  Web Document Conformance Checker (BETA)< Line 11  Web Document Conformance Checker (BETA)<
11  <body>  <body>
12  <h1>Description of Errors</h1>  <h1>Description of Errors</h1>
13    
14  <section id="html5-parse-errors">  <section id="html5-character-encoding">
15  <h2>HTML5 Parse Errors</h2>  <h2>HTML5 Character Encoding Errors</h2>
16    
17  <d:item name="after head"  <d:item name="character encoding" class="format-charset must" level="m">
18      <d:message xml:lang="en">Character encoding <code><var>$0</var></code>
19      is not allowed for <abbr>HTML</abbr> document.</d:message>
20      <d:desc xml:lang="en">
21        <p>The character encoding used for the document is not allowed
22        for <abbr>HTML</abbr> document.  The document is non‐conforming.</p>
23      </d:desc>
24    </d:item>
25    
26    <d:item name="character encoding" class="format-charset should"
27        level="s">
28      <d:message xml:lang="en">Character encoding <code><var>$0</var></code>
29      should not be used for <abbr>HTML</abbr> document.</d:message>
30      <d:desc xml:lang="en">
31        <p>The character encoding used for the document is not recommended
32        for <abbr>HTML</abbr> document.  The document is non‐conforming
33        unless there is any good reason to use that encoding.</p>
34      </d:desc>
35    </d:item>
36    
37    <d:item name="character encoding" class="format-charset warning"
38        level="w">
39      <d:message xml:lang="en">Use of UTF-8 is encouraged.</d:message>
40      <d:desc xml:lang="en">
41        <p>Use of UTF-8 as the character encoding of the document is encouraged,
42        though the use of another character encoding is still conforming.</p>
43      </d:desc>
44    </d:item>
45    
46    <d:item name="character encoding" class="format-charset unsupported"
47        level="unsupported">
48      <d:message xml:lang="en">Conformance for character encoding requirements
49      cannot be checked.</d:message>
50      <d:desc xml:lang="en">
51        <p>The conformance checker cannot detect whether the input document
52        met the requirements on character encoding, since the document
53        is not inputed as a serialized byte sequence.  The document is
54        not conforming if it is not encoded in an appropriate character
55        encoding with appropriate labeling.</p>
56      </d:desc>
57    </d:item>
58    
59    <d:item name="no character encoding declaration" class="format-charset error"
60        level="m">
61      <d:message xml:lang="en">There is no character encoding
62      declaration.</d:message>
63      <d:desc xml:lang="en">
64        <p>The document does not contain a character encoding
65        declaration.  Unless the character encoding is explicitly
66        specified in lower‐level protocol, e.g. in <abbr>HTTP</abbr>,
67        or is implied by <abbr>BOM</abbr>, there must be a character
68        encoding declaration.  The document is non‐conforming.</p>
69    
70        <p>The long character encoding declaration syntax
71        <code class="html bad example">&lt;meta http-equiv="Content-Type" content="text/html; charset=<var>charset-name</var>"></code>
72        is obsolete.  The new syntax is:</p>
73        <pre class="html example"><code>&lt;meta charset="<var>charset-name</var>"></code></pre>
74    
75        <p>Note that the <code>encoding</code> declaration in <abbr>XML</abbr>
76        declaration has no effect for <abbr>HTML</abbr> document.</p>
77      </d:desc>
78    </d:item>
79    
80    <d:item name="non ascii superset" class="format-charset error"
81        level="m">
82      <d:message xml:lang="en">No character encoding metadata is found
83      in lower‐level protocol nor is there <abbr>BOM</abbr>, while
84      character encoding <code><var>$0</var></code>
85      is not a superset of <abbr>ASCII</abbr>.</d:message>
86      <d:desc xml:lang="en">
87        <p>The document is not labeled with character encoding name
88        in lower‐level protocol, e.g. in <abbr>HTTP</abbr>, and
89        the document is not begin with <abbr>BOM</abbr>.  In addition,
90        the character encoding of the document is not a superset of
91        <abbr>ASCII</abbr>.  The document is non‐conforming.</p>
92    
93        <p>Unless there is a <abbr>BOM</abbr>, the character encoding
94        for the document must be specified in e.g. <abbr>HTTP</abbr>‐level,
95        as:</p>
96        <pre class="http example"><code>Content-Type: text/html; charset=<var>charset-name</var></code></pre>
97    
98        <p>Existence of <abbr>HTML</abbr> character encoding declaration, i.e.
99        <code class="html example">&lt;meta charset="<var>charset-name</var>"></code>,
100        does not allow to omit <code>charset</code> parameter
101        for <abbr>HTML</abbr> document encoded in non‐<abbr>ASCII</abbr>
102        compatible encoding.</p>
103    
104        <p>Character encodings <code>Shift_JIS</code>, <code>Windows-31J</code>,
105        and <code>ISO-2022-JP</code> are <em>not</em> a superset of
106        <abbr>ASCII</abbr> for the purpose of <abbr>HTML</abbr> conformance.</p>
107      </d:desc>
108    </d:item>
109    
110    <d:item name="charset label detected" class="format-charset warning"
111        level="w">
112      <d:message xml:lang="en">While parsing the document as
113      <code><var>$0</var></code>, a character encoding declaration specifying
114      character encoding as <code><var>$1</var></code> is found.  The document
115      is reparsed.</d:message>
116      <d:desc xml:lang="en">
117        <p>While parsing a document in a character encoding,
118        a character encoding declaration which declares the character
119        encoding of the document as another character encoding is found.
120        The occurence of this warning itself does not make the document
121        non‐conforming.  However, the failure of the first attempt to
122        to detect the character encoding might be a result of non‐conformance
123        of the document.</p>
124    
125        <p>The document will be reparsed from the beginning.  Some error
126        or warning might be reported again.</p>
127    
128        <p>These are suggestions to avoid this warning:</p>
129        <ul>
130        <li>Specify <code>charset</code> parameter in the <code>Content-Type</code>
131        field in the <abbr>HTTP</abbr> header, as:
132        <pre class="HTTP example"><code>Content-Type: text/html; charset="<var>charset-name</var>"</code></pre></li>
133        <li>Put the character encoding declaration
134        (<code class="html example">&lt;meta charset="<var>charset-name</var>"></code>)
135        just after <code class="html example">&lt;head></code> start tag.</li>
136        <li>Use <code>UTF-8</code>.</li>
137        </ul>
138      </d:desc>
139    </d:item>
140    </section>
141    
142    <section id="html5-tokenize-error">
143    <h2>HTML5 Parse Errors in Tokenization Stage</h2>
144    
145    <d:item name="after html"
146      class="parse-error">      class="parse-error">
147    <d:message xml:lang="en">The <code><var>$0</var></code> element cannot be    <d:message xml:lang="en">Tag <code>&lt;<var>$0</var>&gt;</code>
148    inserted between <code>head</code> and <code>body</code> elements.</d:message>    is not allowed after the end tag <code>&lt;/html></code>.</d:message>
149    <d:desc xml:lang="en">    <d:desc xml:lang="en">
150      <p>A start tag occurs after the <code>head</code> element is closed      <p>The start or end tag of an element appears after the
151      but before the <code>body</code> element is opened.      <code>html</code> element has been closed.  The document is
152        non-conforming.</p>
153    
154        <p>Any content of the document other than comments
155        must be put into the <code>html</code> element.</p>
156      </d:desc>
157    </d:item>
158    
159    <d:item name="after body"
160        class="parse-error">
161      <d:message xml:lang="en">Tag <code>&lt;<var>$0</var>&gt;</code>
162      is not allowed after the end tag <code>&lt;/body></code>.</d:message>
163      <d:desc xml:lang="en">
164        <p>The start or end tag of an element appears after the
165        <code>body</code> element has been closed.  The document is
166        non-conforming.</p>
167    
168        <p>Any content of the document other than <code>head</code>
169        contents and comments must be put into the <code>body</code>
170        element.</p>
171      </d:desc>
172    </d:item>
173    
174    <d:item name="bare ero"
175        class="tokenize-error">
176      <d:message xml:lang="en">The <code>&amp;</code> character must
177      be escaped as <code class="html example">&amp;amp;</code>.</d:message>
178      <d:desc xml:lang="en">
179        <p>An <code>&amp;</code> character which
180        is not part of any reference appears in the input stream.
181        The document is non‐conforming.</p>
182    
183        <p><em>Any <code>&amp;</code> character in URI (or IRI)
184        must be escaped as <code class="example">&amp;amp;</code>.</em></p>
185    
186        <p>The <code>&amp;</code> character must
187        be the first character of a reference:
188          <dl class="switch">
189          <dt>Named entity reference</dt>
190              <dd><pre class="html example"><code>&amp;<var>entity-name</var>;</code></pre>
191              where <var>entity-name</var> is the name of the
192              character entity to be referenced.</dd>
193          <dt>Numeric character reference</dt>
194              <dd><pre class="html example"><code>&amp;#<var>d</var>;</code></pre>
195              where <var>d</var> is the decimal representation of
196              the code position of the character to be referenced.</dd>
197          <dt>Hexadecimal character reference</dt>
198              <dd><pre class="html example"><code>&amp;#x<var>h</var>;</code></pre>
199              where <var>h</var> is the hexadecimal representation
200              of the code position of the character to be referenced.</dd>
201          </dl>
202        </p>
203    
204        <p>To represent <code>&amp;</code> as a data character, use
205        named entity reference:
206          <pre class="html example"><code>&amp;amp;</code></pre>
207        </p>
208      </d:desc>
209    </d:item>
210    
211    <d:item name="bare etago"
212        class="tokenize-error">
213      <d:message xml:lang="en">A <code>&lt;/</code> string is not followed
214      by a tag name.</d:message><!-- </ EOF -->
215      <d:desc xml:lang="en">
216        <p>There is a <code>&lt;</code> (<code>U+003C</code>
217        <code class="charname">LESS-THAN SIGN</code>) character
218        immediately followed by a <code>/</code> (<code>U+005F</code>
219        <code>SOLIDUS</code>) character, which is not part
220        of any end tag, in the input stream.  The document
221        is non-conforming.</p>
222    
223        <p>The <code>&lt;/</code> sequence immediately followed
224        by an <abbr title="End of file pseudo-character">EOF</abbr> is
225        interpreted as a string data of <code>&lt;/</code>.</p>
226    
227        <p>The <code>&lt;/</code> sequence as string data must
228        be escaped as:
229        <pre class="html example"><code>&amp;lt;/</code></pre>
230        </p>
231      </d:desc>
232    </d:item>
233    
234    <d:item name="bare stago"
235        class="tokenize-error">
236      <d:message xml:lang="en">A <code>&lt;</code> character is not followed
237      by tag name or by a <code>!</code> character.</d:message>
238      <d:desc xml:lang="en">
239        <p>A <code>&lt;</code> (<code>U+003C</code>
240        <code class="charname">LESS-THAN SIGN</code>) character which is not part
241        of any markup appears in the input stream.</p>
242    
243        <p>The <code>&lt;</code> character as a data character must
244        be escaped as:
245        <pre class="html example"><code>&amp;lt;</code></pre>
246        </p>
247      </d:desc>
248    </d:item>
249    
250    <d:item name="bare nero"
251        class="tokenize-error">
252      <d:message xml:lang="en">The decimal representation of the code position
253      of a character must be specified after <code>&amp;#</code>.</d:message>
254      <d:desc xml:lang="en">
255        <p>An <code>&amp;</code> (<code>U+0026</code>
256        <code class="charname">AMPERSAND</code>) character immediately
257        followed by a <code>#</code> (<code>U+0023</code>
258        <code>NUMBER SIGN</code>) character which
259        is not part of any reference appears in the input stream.
260      The document is non-conforming.</p>      The document is non-conforming.</p>
261    
262        <p>The string <code>&amp;#</code> must be the first two characters
263        of a reference:
264          <dl class="switch">
265          <dt>Numeric character reference</dt>
266              <dd><pre class="html example"><code>&amp;#<var>d</var>;</code></pre>
267              where <var>d</var> is the decimal representation of
268              the code point of the character to be referenced.</dd>
269          <dt>Hexadecimal character reference</dt>
270              <dd><pre class="html example"><code>&amp;#x<var>h</var>;</code></pre>
271              where <var>h</var> is the hexadecimal representation
272              of the code point of the character to be referenced.</dd>
273          </dl>
274        </p>
275    
276        <p>To represent <code>&amp;#</code> as data characters, use
277        a named entity reference for the <code>&amp;</code> character:
278          <pre class="html example"><code>&amp;amp;#</code></pre>
279        </p>
280      </d:desc>
281    </d:item>
282    
283    <d:item name="bare hcro"
284        class="tokenize-error">
285      <d:message xml:lang="en">The hexadecimal representation of the code position
286      of a character must be specified after <code>&amp;#x</code>.</d:message>
287      <d:desc xml:lang="en">
288       <p>The string <code>&amp;#x</code> or <code>&amp;#X</code> which
289       is not part of any reference appears in the input stream.
290        The document is non-conforming.</p>
291    
292        <p>The string <code>&amp;#x</code> or <code>&amp;#X</code> must
293        be the first three characters of a hexadecimal reference:
294          <pre class="html example"><code>&amp;#x<var>h</var>;</code></pre>
295        where <var>h</var> is the hexadecimal representation
296        of the code point of the character to be referenced.</p>
297    
298        <p>To represent <code>&amp;#x</code> as data characters, use
299        a named entity reference for the <code>&amp;</code> character:
300          <pre class="html example"><code>&amp;amp;#x</code></pre>
301        </p>
302      </d:desc>
303    </d:item>
304    
305    <d:item name="bogus comment"
306        class="tokenize-error">
307      <d:message xml:lang="en">String <code>&lt;!</code> is not followed
308      by <code>--</code>.</d:message>
309      <d:desc xml:lang="en">
310        <p>There is a <code>&lt;</code> (<code>U+003C</code>
311        <code class="charname">LESS-THAN SIGN</code>) character
312        followed by a <code>!</code> (<code>U+0021</code>
313        <code class="charname">EXCLAMATION MARK</code>) character,
314        which is not followed by a <code>--</code> or
315        <code>!DOCTYPE</code>.  The document is non-conforming.</p>
316    
317        <dl class="switch">
318        <dt>Comments</dt>
319          <dd>In HTML document, comments must be introduced by
320          <code class="example">&lt;!--</code> (<code>&lt;!</code>
321          <em>immediately</em> followed
322          by <em>two</em> <code>-</code>s) and must be terminated by
323          <code class="example">--></code>.
324          Strings <code>&lt;!</code> not followed
325          by <code>--</code> and <code>&lt;!-</code> not followed by
326          <code>-</code> are not valid open delimiters for comments.</dd>
327        <dt>Marked sections, including <code>CDATA</code> sections</dt>
328          <dd>Marked sections are not allowed in HTML document.</dd>
329        <dt>Markup declarations</dt>
330          <dd>Markup declarations, except for <code>DOCTYPE</code>
331          and comment declarations, are not allowed in HTML document.</dd>
332        <dt>String <code>&lt;!</code></dt>
333          <dd>String <code>&lt;!</code> must be escaped as
334          <code class="example">&amp;lt;!</code>.</dd>
335        </dl>
336      </d:desc>
337    </d:item>
338    
339    <d:item name="bogus end tag"
340        class="tokenize-error">
341      <d:message xml:lang="en">String <code>&lt;/</code> is not followed
342      by tag name.</d:message><!-- </ non-name-start-char-non-EOF -->
343      <d:desc xml:lang="en">
344        <p>There is a <code>&lt;</code> (<code>U+003C</code>
345        <code class="charname">LESS-THAN SIGN</code>) character
346        immediately followed by a <code>/</code> (<code>U+005F</code>
347        <code>SOLIDUS</code>) character, which is not part
348        of any end tag, in the input stream.  The document
349        is non-conforming.</p>
350    
351        <p>The <code>&lt;/</code> sequence not followed by a
352        tag name is parsed as an opening of bogus comment.</p>
353    
354        <p>The <code>&lt;/</code> sequence as string data must
355        be escaped as:
356        <pre class="html example"><code>&amp;lt;/</code></pre>
357        </p>
358      </d:desc>
359    </d:item>
360    
361    <d:item name="dash in comment"
362        class="tokenize-error">
363      <d:message xml:lang="en">There is a <code>--</code> sequence
364      in a comment.</d:message>
365      <d:desc xml:lang="en">
366        <p>There is a <code>-</code> (<code>U+002D</code>
367        <code class="charname">HYPHEN-MINUS</code>) character
368        at the end of the comment or a <code>--</code> sequence
369        in the comment.  The document is non-conforming.</p>
370    
371        <p>Comments cannot contain a string <code>--</code>, as in XML.
372        Unlike SGML, there cannot be more than one comments
373        (where <i>comment</i> is an SGML term) in the comment
374        declaration.</p>
375    </d:desc>    </d:desc>
376  </d:item>  </d:item>
377    
378  <d:item name="duplicate attribute"  <d:item name="duplicate attribute"
379      class="tokenize-error">      class="tokenize-error">
380    <d:message xml:lang="en">There are two attributes with same name.</d:message>    <d:message xml:lang="en">There are two attributes with name
381          <code><var>$0</var></code>.</d:message>
382    <d:desc xml:lang="en">    <d:desc xml:lang="en">
383      <p>Attributes must be unique in an element.  Specifying      <p>There are more than one attributes with the same
384      attributes with same name more than once is non-conforming.</p>      name in a tag.  The document is non-conforming.</p>
385    
386      <p>The <code>motion</code> attribute is not part of the HTML standard.      <p>The <code>motion</code> attribute is not part of the HTML standard.
387      Use <code>img</code> element with animation GIF instead.</p>      Use <code>img</code> element with animation GIF instead.</p>
# Line 39  Web Document Conformance Checker (BETA)< Line 390  Web Document Conformance Checker (BETA)<
390    
391  <d:item name="nestc"  <d:item name="nestc"
392      class="tokenize-error">      class="tokenize-error">
393    <d:message xml:lang="en">Void element syntax (<code>/></code>) cannot be    <d:message xml:lang="en">Polytheistic slash (<code>/></code>) cannot be
394    used for this element.</d:message>    used for this element.</d:message>
395    <d:desc xml:lang="en">    <d:desc xml:lang="en">
396      <p>The void element syntax <code>/></code> syntax can only be      <p>Polytheistic slash (<code>/></code>) must not be used
397        for the element.  The document is non-conforming.</p>
398    
399        <p>The polytheistic slash can only be
400      used for <code>base</code>, <code>link</code>, <code>meta</code>,      used for <code>base</code>, <code>link</code>, <code>meta</code>,
401      <code>hr</code>, <code>br</code>, <code>img</code>,      <code>hr</code>, <code>br</code>, <code>img</code>,
402      <code>embed</code>, <code>param</code>, <code>area</code>,      <code>embed</code>, <code>param</code>, <code>area</code>,
403      <code>col</code>, and <code>input</code> elements.      <code>col</code>, and <code>input</code> elements.</p>
404      For any other elements, using that syntax is non-conforming.</p>  
405        <dl class="switch">
406        <dt><code>&lt;script/></code></dt>
407            <dd><p>The polytheistic slash cannot be used for <code>script</code>
408            element.  Even for an empty <code>script</code> element,
409            there must be an explicit end tag
410            <code class="html example">&lt;/script></code>.</p>
411    
412            <p><strong>NOTE</strong>: Though some user agents interpret
413            polytheistic slash for <code>script</code> element as the
414            closing of the element, such usage is not allowed under
415            the current standard.</p></dd>
416        <dt><code>&lt;basefont/></code>, <code>&lt;bgsound/></code>,
417        <code>&lt;frame/></code>, <code>&lt;keygen/></code>,
418        <code>&lt;spacer/></code>, <code>&lt;wbr/></code></dt>
419            <dd>These elements are themselves non-conforming.</dd>
420        <!-- isindex, image -->
421        <dt><code>&lt;command/></code>, <code>&lt;event-source/></code>,
422        <code>&lt;nest/></code>, or <code>&lt;source/></code></dt>
423            <dd>Future revision of HTML5 parsing algorithm is expected
424            to allow polytheistic slash for these elements.</dd>
425        <dt><code>&lt;a/></code>, <code>&lt;p/></code></dt>
426            <dd>These elements are not always empty and therefore
427            polytheistic slash is not allowed.  Use explicit end tag
428            to represent empty element as:
429              <pre class="example html"><code>&lt;p>&lt;/p></code></pre>
430            </dd>
431        </dl>
432    
433      <p>Unlike XML, the void element syntax (<code>/></code>) has      <p>Note that, unlike in XML, the polytheistic slash has
434      no effect in HTML.</p>      no effect in HTML.</p>
435    </d:desc>    </d:desc>
436  </d:item>  </d:item>
437    
438    
439    <d:item name="pio"
440        class="tokenize-error">
441      <d:message xml:lang="en">Processing instruction
442      (<code>&lt;?<var>...</var>></code>) cannot be used.</d:message>
443      <d:desc xml:lang="en">
444        <p>Processing instructions (<code>&lt;?<var>...</var>?></code>),
445        including XML declaration (<code>&lt;?xml <var>...</var>?></code>)
446        and XML style sheet <abbr title="processing instruction">PI</abbr>
447        (<code>&lt;?xml-stylesheet <var>...</var>?></code>), are not allowed
448        in the HTML syntax.  The document is non-conforming.</p>
449    
450        <dl class="switch">
451        <dt><code>&lt;?xbl?></code> (<abbr>XBL</abbr> Association)</dt>
452          <dd>An <abbr>XBL</abbr> binding cannot be associated by
453          <abbr title="processing instruction">PI</abbr> in <abbr>HTML</abbr>
454          document.  Use <code>binding</code> property in <abbr>CSS</abbr>
455          style sheet as:
456            <pre class="html example"><code>&lt;style>
457    p {
458      binding: url(binding.xbl);
459    }
460    &lt;/style></code></pre>
461          </dd>
462        <dt><code>&lt;?xml?&gt;</code> (XML declaration)</dt>
463            <dd>XML declaration is unnecessary for HTML documents.</dd>
464        <dt><code>&lt;?xml-stylesheet?></code> (XML style sheet
465        <abbr title="processing instruction">PI</abbr>)</dt>
466            <dd>Use HTML <code>link</code> element with <code>rel</code>
467            attribute set to <code>stylesheet</code> (or,
468            <code>alternate stylesheet</code> for an alternate style
469            sheet).
470              <pre class="example html"><code>&lt;link rel=stylesheet href="path/to/stylesheet.css"></code></pre>
471            </dd>
472        <dt><code>&lt;?php?&gt;</code> or
473        <code>&lt;? <var>... <abbr>PHP</abbr> code ...</var> ?&gt;</code>
474        (<abbr>PHP</abbr> code)</dt>
475            <dd>The conformance checker does <em>not</em> support
476            checking for PHP source documents.</dd>
477        <dt>Other processing instructions</dt>
478            <dd>Processing instructions cannot be inserted in an HTML
479            document.  Use XML document or insert
480            <code>ProcessingInstruction</code> node by scripting.</dd>
481        </dl>
482    
483        <p>Web browsers will parse processing instructions as bogus
484        comments.  Some legacy Web browsers, such as IE:mac and
485        some mobile Web browsers, will display processing instructions
486        as string.</p>
487      </d:desc>
488    </d:item>
489    
490    </section>
491    
492    <section id="html5-parse-errors">
493    <h2>HTML5 Parse Errors in Tree Construction Stage</h2>
494    
495    <d:item name="after head"
496        class="parse-error">
497      <d:message xml:lang="en">The <code><var>$0</var></code> element cannot be
498      inserted between <code>head</code> and <code>body</code> elements.</d:message>
499      <d:desc xml:lang="en">
500        <p>A start tag appears after the <code>head</code> element is closed
501        but before the <code>body</code> element is opened.
502        The document is non-conforming.</p>
503      </d:desc>
504    </d:item>
505    
506    <d:item name="DOCTYPE in the middle"
507        class="parse-error">
508      <d:message xml:lang="en">A <code>DOCTYPE</code> appears after any
509      element or data character has been seen.</d:message>
510      <d:desc xml:lang="en">
511        <p>A <code>DOCTYPE</code> appears after any element or data character
512        has been seen.  The document is non-conforming.</p>
513        
514        <p>The <code>DOCTYPE</code> must be placed before any
515        tag, reference, or data character.  Only white space characters
516        and comments can be inserted before the <code>DOCTYPE</code>.</p>
517      </d:desc>
518    </d:item>
519    
520    <d:item name="in a:a"
521        class="parse-error">
522      <d:message xml:lang="en">Anchor cannot be nested.</d:message>
523      <d:desc xml:lang="en">
524        <p>HTML <code>a</code> elements cannot be nested.
525        The document is non-conforming.</p>
526    
527        <p>In the HTML syntax, a start tag of the <code>a</code>
528        implies the end tag of any opening <code>a</code> element.</p>
529      </d:desc>
530    </d:item>
531    
532    <d:item name="in body"
533        class="parse-error">
534      <d:message xml:lang="en">Tag <code>&lt;<var>$0</var>&gt;</code>
535      is not allowed in the <code>body</code> element.</d:message>
536      <d:desc xml:lang="en">
537        <p>The start or end tag of an element, which
538        cannot be a descendant of <code>body</code> element, appears
539        in the input stream while the <code>body</code> element has been opened.
540        The document is non-conforming.</p>
541      </d:desc>
542    </d:item>
543    
544    <d:item name="in head:head"
545        class="parse-error">
546      <d:message xml:lang="en">Start tag <code>&lt;head&gt;</code>
547      is not allowed in the <code>head</code> element.</d:message>
548      <d:desc xml:lang="en">
549        <p>There is a start tag <code>&lt;head></code> in the
550        <code>&lt;head></code> element.  The document is non-conforming.</p>
551    
552        <p>In an HTML document there must not be more than
553        one <code>head</code> element, therefore no more than one
554        start tag <code>&lt;head></code> can appear in the input stream.</p>
555      </d:desc>
556    </d:item>
557    
558    <d:item name="in table"
559        class="parse-error">
560      <d:message xml:lang="en">Tag <code>&lt;<var>$0</var>&gt;</code>
561      is not allowed in a <code>table</code> element.</d:message>
562      <d:desc xml:lang="en">
563        <p>The start or end tag of an element, which
564        cannot be a child of <code>table</code> element, appears
565        in the input stream while the <code>table</code> element has been opened
566        but no other element has been opened.  The document is non-conforming.</p>
567    
568        <p>In <code>table</code>, only table related elements
569        are allowed; any other element must be contained in
570        <code>td</code> or <code>th</code> element to form
571        a part of the table, or <code>caption</code> element to create
572        a table caption.</p>
573      </d:desc>
574    </d:item>
575    
576    <d:item name="in table:#character"
577        class="parse-error">
578      <d:message xml:lang="en">Data character is not allowed in
579      <code>table</code>.</d:message>
580      <d:desc xml:lang="en">
581        <p>A data character appears in <code>table</code>.  The document
582        is non-conforming.</p>
583    
584        <p>In <code>table</code>, only table related elements
585        are allowed; any other element and data character must be contained in
586        <code>td</code> or <code>th</code> element to form
587        a part of the table, or <code>caption</code> element to create
588        a table caption.</p>
589      </d:desc>
590    </d:item>
591    
592    <d:item name="missing start tag:tr"
593        class="parse-error">
594      <d:message xml:lang="en">Start tag of <code>tr</code>
595      element is missing.</d:message>
596      <d:desc>
597        <p>Start tag of a <code>tr</code> element, which is <em>not</em>
598        optional, is missing.  The document is non-conforming.</p>
599    
600        <p>In a table section, a <code>&lt;tr></code> start tag
601        must occur before any <code>&lt;td></code> or
602        <code>&lt;th></code> start tag.  Though the HTML5 parser
603        implies the <code>&lt;tr></code> start tag before
604        these start tags, it must be explicitly specified.</p>
605      </d:desc>
606    </d:item>
607    
608    <d:item name="no DOCTYPE"
609        class="parse-error">
610      <d:message xml:lang="en">This document does not start with a
611      <code>DOCTYPE</code>.</d:message>
612      <d:desc>
613        <p>The document does not start with a <code>DOCTYPE</code>.
614        The document is non-conforming.</p>
615    
616        <p>An HTML document must start by a <code>DOCTYPE</code>:
617          <pre class="html example"><code>&lt;!DOCTYPE HTML></code></pre>
618        </p>
619    
620        <p>Only white space characters and comments are allowed
621        before the <code>DOCTYPE</code>.  XML declaration is <em>not</em>
622        allowed in HTML document.</p>
623      </d:desc>
624    </d:item>
625    
626    <d:item name="not closed"
627        class="parse-error">
628      <d:message xml:lang="en">Element <code><var>$0</var></code> is not
629      closed.</d:message>
630      <d:desc>
631        <p>End tag of an element is not found before, for example,
632        an end tag of another element appears or
633        the end of the document.  The document is non-conforming.</p>
634    
635        <p>Only <code>body</code>, <code>colgroup</code>, <code>dd</code>,
636        <code>dt</code>, <code>head</code>, <code>html</code>, <code>li</code>,
637        <code>ol</code>, <code>option</code>, <code>optgroup</code>,
638        <code>p</code>, <code>rb</code>, <code>rp</code>, <code>rt</code>,
639        <code>tbody</code>, <code>td</code>, <code>tfoot</code>,
640        <code>th</code>, <code>thead</code>, <code>tr</code>,
641        <code>ul</code> end tag can be omitted in HTML documents.
642        For any element except for void element, there must be an explicit
643        end tag.</p>
644    
645        <dl class="switch">
646        <dt>HTML <code>canvas</code> element</dt>
647          <dd>Though the element is void in earlier versions of Safari,
648          the <code>canvas</code> element is <em>no</em> longer
649          defined as empty.  There must be an end tag
650          <code class="html example">&lt;/canvas></code>.</dd>
651        </dl>
652    
653        <p>Note that misnesting tags, such as
654        <code class="bad example">&lt;a>&lt;b>&lt;/a>&lt;/b></code>, are not
655        allowed and they also cause this error.</p>
656      </d:desc>
657    </d:item>
658    
659    <d:item name="not first start tag"
660        class="parse-error">
661      <d:message xml:lang="en">This <code>&lt;html></code> tag is not
662      the first start tag.</d:message>
663      <d:desc>
664        <p>There is a start tag of the <code>html</code> element
665        that it not the first start tag in the input stream.
666        The document is non-conforming.</p>
667    
668        <p>In an HTML document, there cannot be more than one
669        <code>html</code> element and therefore there cannot be
670        more than one <code>&lt;html></code> tag.  In addition,
671        nothing can be placed before the <code>&lt;html></code> tag
672        except a <code>DOCTYPE</code>, white space characters,
673        and comments.</p>
674      </d:desc>
675    </d:item>
676    
677    <d:item name="not HTML5"
678        class="parse-error">
679      <d:message xml:lang="en">This document is written in an old version of
680      HTML.</d:message>
681      <d:desc xml:lang="en">
682        <p>The document contains a <code>DOCTYPE</code> declaration
683        that is different from HTML5 <code>DOCTYPE</code> (i.e.
684        <code class="example html">&lt;!DOCTYPE HTML&gt;</code>).
685        The document is non‐conforming.</p>
686    
687        <p>The document might or might not be conformant to
688        some version of HTML.  However, conformance to any HTML
689        specification other than HTML5 provides for no practical
690        convenience, since Web borwsers will parse any
691        HTML document (roughly) as defined in HTML5.</p>
692      </d:desc>
693    </d:item>
694    
695    <d:item name="unmatched end tag"
696        class="parse-error">
697      <d:message xml:lang="en">Element <code><var>$0</var></code> is not
698      opened.</d:message>
699      <d:desc>
700        <p>An end tag appears though no element with the same name
701        has been opened.  The document is non-conforming.</p>
702    
703        <p>For any end tag in HTML document, there must be a
704        corresponding start tag.</p>
705    
706        <dl class="switch">
707        <dt>HTML <code>base</code>, <code>basefont</code>,
708        <code>bgsound</code>, <code>br</code>, <code>col</code>,
709        <code>embed</code>, <code>frame</code>, <code>hr</code>,
710        <code>image</code>, <code>img</code>, <code>input</code>,
711        <code>isindex</code>, <code>link</code>, <code>meta</code>,
712        <code>param</code>, <code>spacer</code>, or <code>wbr</code> element</dt>
713          <dd>End tag is not allowed for these elements, since
714          those content must always be empty.  Remove end tag.</dd>
715        <!-- keygen -->
716        <!-- command, event-source, nest, source -->
717        </dl>
718      </d:desc>
719    </d:item>
720    
721  </section>  </section>
722    
723  <section id="element-content-model-errors">  <section id="element-content-model-errors">
# Line 64  Web Document Conformance Checker (BETA)< Line 728  Web Document Conformance Checker (BETA)<
728    <d:message xml:lang="en">Data character is not allowed in this    <d:message xml:lang="en">Data character is not allowed in this
729    context.</d:message>    context.</d:message>
730    <d:desc xml:lang="en">    <d:desc xml:lang="en">
731      <p>A data character occurs where it is not allowed in this      <p>A data character appears where it is not allowed in this
732      context.  The document is non-conforming.</p>      context.  The document is non-conforming.</p>
733    
734      <p>Possible causes:      <p>Possible causes:
735        <dl>        <ul>
736        <dt>If the erred element is an inline-level element (such        <li><p>A data character cannot be a child
737        as <code>a</code> or <code>span</code>)</dt>        of certain sectioning elements such as <code>body</code>,
738            <dd><p>A data character cannot be a child        <code>section</code>, and <code>blockquote</code>.</p>
739            of certain sectioning elements such as <code>body</code>,  
740            <code>section</code>, and <code>blockquote</code>.</p>        <p>Any inline-level content must be put
741          in e.g. paragraph element such as <code>p</code>.</p></li>
742            <p>Any inline-level content must be put        <li><p>Though some elements such as <code>div</code>,
743            in e.g. paragraph element such as <code>p</code>.</p></dd>        <code>li</code>, and <code>td</code> allow
744        <dt>If the erred element is a block-level element (such as        <em>either one</em> of block-level or inline-level content
745        <code>div</code> or <code>h<var>n</var></code>)</dt>        is allowed.  If there is a block-level content,
746            <dd><p>Though some elements such as <code>div</code>,        any inline-level content must be put
747            <code>li</code>, and <code>td</code> allow        in e.g. paragraph element such as <code>p</code>.</p></li>
748            <em>either one</em> of block-level or inline-level content        </ul>
           is allowed.  If there is a block-level content,  
           any inline-level content must be put  
           in e.g. paragraph element such as <code>p</code>.</p></dd>  
       </dl>  
749      </p>      </p>
750    </d:desc>    </d:desc>
751  </d:item>  </d:item>
# Line 97  Web Document Conformance Checker (BETA)< Line 757  Web Document Conformance Checker (BETA)<
757    <d:desc xml:lang="en">    <d:desc xml:lang="en">
758      <p>The content model of the element is so defined that it      <p>The content model of the element is so defined that it
759      must contain a <code><var>$0</var></code> child element.      must contain a <code><var>$0</var></code> child element.
760      Without such an element, the document is non-conforming.</p>      The document is non-conforming.</p>
761    
762      <p>For example:      <dl class="switch">
763        <ul>      <dt>HTML <code>head</code> element</dt>
764        <li>The <code>head</code> element must contain exactly one        <dd>There must be a <code>title</code> child element.</dd>
765        <code>title</code> child element.</li>      <dt>HTML <code>html</code> element</dt>
766        <li><a href="#child-element-missing:td%7Cth">The <code>tr</code>        <dd>There must be a <code>head</code> child element followed
767        element must contain one or more <code>td</code> or <code>th</code>        by a <code>body</code> element.</dd>
768        child element.</a></li>      <dt>HTML <code>tr</code> element</dt>
769        </ul>        <dd><a href="#child-element-missing:td%7Cth">There must be
770      </p>        one or more <code>td</code> or <code>th</code> child element.</a></dd>
771        </dl>
772    </d:desc>    </d:desc>
773  </d:item>  </d:item>
774    
# Line 117  Web Document Conformance Checker (BETA)< Line 778  Web Document Conformance Checker (BETA)<
778    or <code>th</code> element as a child of this element.</d:message>    or <code>th</code> element as a child of this element.</d:message>
779    <d:desc xml:lang="en">    <d:desc xml:lang="en">
780      <p>The <code>tr</code> element must contain at least one      <p>The <code>tr</code> element must contain at least one
781      <code>td</code> or <code>th</code> child element.  Without      <code>td</code> or <code>th</code> child element.  The document
782      such an element, the document is non-conforming.</p>      is non-conforming.</p>
783    </d:desc>    </d:desc>
784  </d:item>  </d:item>
785    
# Line 127  Web Document Conformance Checker (BETA)< Line 788  Web Document Conformance Checker (BETA)<
788    <d:message xml:lang="en">This element is not allowed in this    <d:message xml:lang="en">This element is not allowed in this
789    context.</d:message>    context.</d:message>
790    <d:desc xml:lang="en">    <d:desc xml:lang="en">
791      <p>An element occurs where it is not allowed.  The document      <p>An element appears where it is not allowed.  The document
792      is non-conforming.</p>      is non-conforming.</p>
793    
794      <p>Possible causes:      <p>Possible causes:
795        <dl>        <dl class="switch">
796        <dt>If the erred element is an inline-level element (such        <dt>If the element with the error is an inline-level element,
797        as <code>a</code> or <code>span</code>)</dt>        such as <code>a</code>, <code>progress</code>, or <code>img</code></dt>
798            <dd><p>An inline-level element cannot be a child            <dd><p>An inline-level element cannot be a child
799            of certain sectioning elements such as <code>body</code>,            of certain sectioning elements such as <code>body</code>,
800            <code>section</code>, and <code>blockquote</code>.</p>            <code>section</code>, and <code>blockquote</code>.</p>
801    
802            <p>Any inline-level content must be put            <p>Any inline-level content must be put
803            in e.g. paragraph element such as <code>p</code>.</p></dd>            in e.g. paragraph element such as <code>p</code>.</p></dd>
804        <dt>If the erred element is a block-level element (such as        <dt>If it is a block-level elements, such as <code>aside</code>,
805        <code>div</code> or <code>h<var>n</var></code>)</dt>        <code>div</code>, <code>h<var>n</var></code>,
806            <dd><p>Though some elements such as <code>div</code>,        <code>p</code>, or <code>section</code></dt>
807            <code>li</code>, and <code>td</code> allow            <dd><dl class="switch">
808            <em>either one</em> of block-level or inline-level content                <dt>If the parent element is <code>div</code>,
809            is allowed.  If there is a block-level content,                <code>li</code>, <code>td</code>, or <code>th</code></dt>
810            any inline-level content must be put                <!-- @@ TODO: more... -->
811            in e.g. paragraph element such as <code>p</code>.</p></dd>                    <!-- @@ TODO: <p><ul><li><p> -->
812        <dt>If the erred element is the root <code>html</code> element</dt>                    <dd><p>The parent element allows <em>either</em>
813            <dd><p>In an XHTML document, the root <code>html</code>                    block-level or inline-level content.  If there is a
814            element must have an <code>xmlns</code> attribute                    block-level content, any inline-level content must be
815            whose value is set to                    put in e.g. paragraph element such as <code>p</code>.</p>
816            <code>http://www.w3.org/1999/xhtml</code>.</p></dd>                    <p>For example, an HTML document fragment
817                      <code class="html bad example">&lt;div>&lt;p>Hello!&lt;/p> World!&lt;/div></code>
818                      is non-conforming, since a word <q>World!</q> does not belong
819                      to any paragraph.  (If not part of any paragraph, what is
820                      it!?)  A conforming example would be:
821                        <pre class="html example"><code>&lt;div>&lt;p>Hello!&lt;/p> &lt;p>World!&lt;/p>&lt;/div></code></pre>
822                      </p></dd>
823                  <dt>If the parent element does <em>not</em> allow
824                  block-level elements as content</dt>
825                      <dd>The element is not allowed to be inserted here.
826                      For example, a <code>div</code> element cannot be
827                      a child of an <code>h1</code> element.</dd>
828              </dl></dd>
829          <dt>If the element with the error is a <code>noscript</code> element</dt>
830              <dd>The <code>noscript</code> element is allowed only in the context
831              where a block-level or inline-level content is expected
832              and in the <code>head</code> element.
833              It cannot be used in e.g. <code>ul</code>, <code>table</code>,
834              or <code>select</code>.</dd>
835          <dt>If the element with the error is <code>blink</code>,
836          <code>center</code>, or <code>marquee</code> element</dt>
837              <dd>These elements are not part of the HTML standard.
838              Use CSS for styling control.</dd>
839    
840          <dt><code>button</code>, <code>datalist</code>,
841          <code>fieldset</code>, <code>form</code>,
842          <code>input</code>, <code>label</code>,
843          <code>optgroup</code>, <code>option</code>, <code>output</code>,
844          <code>rb</code>, <code>rp</code>, <code>rt</code>, <code>ruby</code>,
845          <code>textarea</code>, or <code>textarea</code> element</dt>
846          <!-- rbc, rtc ? -->
847              <dd>These elements are intentionally not supported by the conformance
848              checker <em>yet</em>.</dd>
849        </dl>        </dl>
850      </p>      </p>
851    </d:desc>    </d:desc>
852  </d:item>  </d:item>
853    
854  enumerated:invalid;attribute-error;This attribute only allow a limited set of values and the specified value is not one of them.  <d:item name="element not allowed:root"
855  no DOCTYPE;parse-error;This document does not start with the <code>DOCTYPE</code> declaration.      class="content-model-error">
856  not HTML5;parse-error;This document is written in an old version of HTML.    <d:message xml:lang="en">This element is not allowed as a root
857  not closed;parse-error;Element <code>$0</code> is not closed.    element.</d:message>
858  unmatched end tag;parse-error;Element <code>$0</code> is not opened.    <d:desc xml:lang="en">
859        <p>An element that is not allowed as the root element
860  table:no cell in last row;table-model-error;The table has no cell (<code>td</code> or <code>th</code>) in the last row.      is used as the root element of the document.  The document is
861        non-conforming, as far as the conformance checker can tell.</p>
862  s:IMT:obsolete subtype;should;An <em>obsolete</em> subtype is used.  
863  s:IMT:private subtype;should;A private (<code>x-</code> or <code>x.</code>) subtype is used.      <dl class="switch">
864  s:IMT:unregistered subtype;should;The subtype is not registered to IANA.      <dt><code>html</code> element in an XHTML document</dt>
865            <dd><p>In <abbr>XHTML</abbr> document, the root <code>html</code>
866            element must have an <code>xmlns</code> attribute as:
867              <pre class="xml example"><code>&lt;html xmlns="http://www.w3.org/1999/xhtml"></code></pre></p></dd>
868        <dt><code>rss</code> element</dt>
869            <dd><p>The document is written in some version of RSS.</p>
870            <p>The conformance checker does not support any version
871            of RSS.  Use Atom 1.0 for feed documents.</p></dd>
872        <dt><code>feed</code> element</dt>
873            <dd><p>The Atom <code>feed</code> element must be
874            in the <code>http://www.w3.org/2005/Atom</code>
875            namespace as:
876              <pre class="xml example"><code>&lt;feed xmlns="http://www.w3.org/2005/Atom"></code></pre>
877            </p>
878            <p>The conformance checker does not support Atom 0.3.
879            Use Atom 1.0 for feed documents.</p></dd>
880        </dl>
881      </d:desc>
882    </d:item>
883    
884    <d:item name="ps element missing"
885        class="content-model-error">
886      <d:message xml:lang="en">There is no <code><var>$0</var></code>
887      element before this element.</d:message>
888      <d:desc xml:lang="en">
889        <p>There must be an element before another element, but there
890        is not.  The document is non-conforming.</p>
891    
892        <p>For example, there must be a <code>dt</code> element
893        before any <code>dd</code> element.</p>
894      </d:desc>
895    </d:item>
896    
897    </section>
898    
899    <section id="attribute-errors">
900    <h2>Attribute Errors</h2>
901    
902    <d:item name="attribute missing"
903        class="attribute-error">
904      <d:message xml:lang="en">Required attribute <code><var>$0</var></code>
905      is not specified.</d:message>
906      <d:desc>
907        <p>A required attribute is not specified.  The document
908        is non-conforming.</p>
909    
910        <p>Some attribute is defined as <i>required</i>.
911        Without required attributes specified, user agents
912        cannot provide full functionality of the element to the user.</p>
913    
914        <dl class="switch">
915        <dt>HTML <code>img</code> element</dt>
916            <dd>The <code>src</code> attribute must be specified.
917            Additionally, the <code>alt</code> attribute must be specified
918            in many cases.</dd>
919        <dt>HTML <code>link</code> element</dt>
920            <dd>The <code>rel</code> attribute must be specified.
921            Note that the <code>rev</code> attribute is obsolete.</dd>
922        </dl>
923      </d:desc>
924    </d:item>
925    
926    <d:item name="attribute not allowed" class="attribute-error">
927      <d:message xml:lang="en">Attribute
928      <code><var>{local-name}</var></code> is not allowed for
929      <code><var>{element-local-name}</var></code> element.</d:message>
930      <d:desc xml:lang="en">
931        <p>An attribute is specified where it is not allowed.
932        The document is non-conforming.</p>
933    
934        <dl>
935        <dt>HTML <code>meta</code> element</dt>
936            <dd>For HTML <code>meta</code> element, <em>only one</em> of
937            <code>name</code>, <code>http-equiv</code>, or <code>charset</code>
938            attribute is allowed.</dd>
939        </dl>
940      </d:desc>
941    </d:item>
942    
943    <d:item name="in HTML:xml:lang"
944        class="attribute-error">
945      <d:message xml:lang="en">The <code>xml:lang</code> attribute is not
946      allowed in HTML document.</d:message>
947      <d:desc xml:lang="en">
948        <p>The <code>xml:lang</code> attribute is not allowed in
949        HTML document.  The document is non-conforming.</p>
950    
951        <p>Use of the <code>xml:lang</code> attribute is conforming
952        <em>only</em> in XML documents.</p>
953    
954        <p>To specify natural language information in HTML document,
955        use <code>lang</code> attribute instead.</p>
956    
957        <p>XHTML 1.0 Appendix C was encouraged to specify both
958        <code>lang</code> and <code>xml:lang</code> attributes with
959        the same value.  Such a duplication has <em>no effect</em> in practice.
960        Use only one of <code>lang</code> (in HTML) or <code>xml:lang</code> (in
961        XML).</p>
962    
963        <!-- @@ ISSUE: xml:lang in non-HTML element in DOM5 HTML created
964             from an HTML document? -->
965      </d:desc>
966    </d:item>
967    
968    <d:item name="in XML:charset"
969        class="attribute-error">
970      <d:message xml:lang="en">The <code>charset</code> attribute is not
971      allowed in XML document.</d:message>
972      <d:desc>
973        <p>The <code>charset</code> attribute of a
974        <code>meta</code> element is not allowed in XML document.
975        The document is non-conforming.</p>
976    
977        <p>To specify the character encoding used for serialization,
978        if necessary, use XML declaration instead:
979          <pre class="xml example"><code>&lt;?xml version="1.0" encoding="<var>encoding-name</var>"?></code></pre>
980        </p>
981      </d:desc>
982    </d:item>
983    
984    <d:item name="in XML:lang"
985        class="attribute-error">
986      <d:message xml:lang="en">The <code>lang</code> attribute is not
987      allowed in XML document.</d:message>
988      <d:desc>
989        <p>The HTML <code>lang</code> attribute is not allowed in
990        XML document.  The document is non-conforming.</p>
991    
992        <p>The <code>lang</code> attribute in <code>null</code>
993        namespace for HTML elements is conforming <em>only</em> in
994        HTML documents.</p>
995    
996        <p>To specify natural language information in XML document,
997        use <code>xml:lang</code> attribute instead.</p>
998      </d:desc>
999    </d:item>
1000    
1001    <d:item name="in XML:xmlns"
1002        class="attribute-error">
1003      <d:message xml:lang="en">The <code>xmlns</code> attribute
1004      in the <code>null</code> namespace is not allowed in
1005      XHTML document.  The document is non-conforming.</d:message>
1006      <d:desc>
1007        <p>The <code>xmlns</code> attribute in the <code>null</code>
1008        namespace is not allowed in XHTML document.</p>
1009    
1010        <p>This error should not occur in conformance-checking of
1011        static documents.</p>
1012      </d:desc>
1013    </d:item>
1014    
1015    </section>
1016    
1017    <section id="attribute-value-errors">
1018    <h2>Attribute Value Errors</h2>
1019    
1020    <d:item name="charset:not registered" class="attribute-value-warning warning"
1021        level="w">
1022      <d:message xml:lang="en">Character encoding name <code><var>$0</var></code>
1023      is not registered.</d:message>
1024      <d:desc xml:lang="en">
1025        <p>The specified character encoding name is not registered to
1026        <abbr>IANA</abbr>.  Use of registered character encoding name
1027        is a good practice to facilitate interoperability.</p>
1028    
1029        <dl class="switch">
1030        <dt><code>EUC-TW</code></dt>
1031          <dd><code>EUC-TW</code> is not registered.  Unfortunately, there
1032          is no registered name for that character encoding.  Use
1033          Big5 encoding with character encoding name <code>Big5</code>
1034          if it is enough to represent the document.</dd>
1035        <dt><code>ISO-2022-JP-1</code></dt>
1036          <dd><code>ISO-2022-JP-1</code> is not registered, nevertheless
1037          this character encoding name is documented in
1038          <a href="urn:ietf:rfc:2237"><abbr>RFC</abbr> 2237</a>.  Use
1039          <code>ISO-2022-JP-2</code> instead, since that character encoding
1040          is a superset of ISO-2022-JP-1.</dd>
1041        <dt><code>ISO-2022-JP-3</code>, <code>ISO-2022-JP-3-plane1</code></dt>
1042          <dd>These names are not registered and obsoleted in favor of
1043          <code>ISO-2022-JP-2004</code> and
1044          <code>ISO-2022-JP-2004-plane1</code>.</dd>
1045        <dt><code>ISO-2022-JP-2003</code>,
1046        <code>ISO-2022-JP-2003-plane1</code></dt>
1047          <dd>These names are not registered and corrected to
1048          <code>ISO-2022-JP-2004</code> and
1049          <code>ISO-2022-JP-2004-plane1</code>.</dd>
1050        <dt><code>ISO-2022-JP-2004</code>,
1051        <code>ISO-2022-JP-2004-plane1</code></dt>
1052          <dd>These names are not registered.  Unfortunately, there is
1053          no registered name for these character encodings.</dd>
1054        <dt><code>UTF-8N</code></dt>
1055          <dd><code>UTF-8N</code> is not registered.  Character encoding
1056          name <code>UTF-8</code> represents UTF-8 encoding with or
1057          without <abbr>BOM</abbr>.</dd>
1058        </dl>
1059    
1060        <p><strong>WARNING</strong>: This error might be raised for
1061        a registered character encoding name, since the character encoding
1062        name database of the conformance checker is not complete yet.</p>
1063      </d:desc>
1064    </d:item>
1065    
1066    <d:item name="charset:private" class="attribute-value-warning warning"
1067        level="w">
1068      <d:message xml:lang="en"><code><var>$0</var></code> is a private
1069      character encoding name.</d:message>
1070      <d:desc xml:lang="en">
1071        <p>The specified character encoding name is a private name and
1072        not registered to <abbr>IANA</abbr>.  Use of registered character
1073        encoding name is a good practice to facilitate interoperability.</p>
1074    
1075        <dl class="switch">
1076        <dt><code>x-euc-jp</code></dt>
1077          <dd>Use <code>EUC-JP</code> for the Japanese <abbr>EUC</abbr>
1078          character encoding.</dd>
1079        <dt><code>x-sjis</code></dt>
1080          <dd>Use <code>Shift_JIS</code> for standard Shift encoding scheme of
1081          <abbr>JIS</abbr> coded character set, or <code>Windows-31J</code>
1082          for Microsoft standard character set as implemented by
1083          Microsoft Windows.</dd>
1084        </dl>
1085      </d:desc>
1086    </d:item>
1087    
1088    <d:item name="charset:syntax error" class="attribute-value-error"
1089        level="m">
1090      <d:message xml:lang="en">The specified value is syntactically not a
1091      character encoding name.</d:message>
1092      <d:desc xml:lang="en">
1093        <p>The attribute value must be a character encoding name.  However,
1094        the specified value is not a character encoding name syntactically.
1095        The document is non‐conforming.</p>
1096        <p>Character encoding name is a string of <abbr>ASCII</abbr>
1097        printable characters, up to 40 characters.</p>
1098      </d:desc>
1099    </d:item>
1100    
1101    <d:item name="enumerated:invalid"
1102        class="attribute-value-error">
1103      <d:message xml:lang="en">This attribute only allow a limited set of
1104      values and the specified value <code><var>{@}</var></code> is not one
1105      of them.</d:message>
1106      <d:desc xml:lang="en">
1107        <p>For this attribute only several values are allowed and the
1108        value of the attribute is not one of them.  The document
1109        is non-conforming.</p>
1110    
1111        <dl>
1112        <dt>HTML <code>meta</code> element, <code>http-equiv</code> attribute</dt>
1113            <dd><p>Only values <code>Default-Style</code> and <code>Refresh</code>
1114            are allowed.</p>
1115            <p>Value <code>Content-Type</code> is obsolete; for charset
1116            declaration, the <code>charset</code> attribute can be used as:
1117            <pre class="html example"><code>&lt;meta charset="<var>charset-name</var>"></code></pre>
1118            ... where <var>charset-name</var> is a name of the character encoding
1119            of the document, such as <code>utf-8</code>.</p>
1120            <p>Values <code>Content-Style-Type</code> and
1121            <code>Content-Script-Type</code> are currently not allowed.</p>
1122            <p>Value <code>Keywords</code> is not allowed.  Use
1123            <code>name</code> attribute instead of <code>http-equiv</code>
1124            attribute.</p>
1125            <p>Values <code>Expires</code>, <code>Pragma</code>,
1126            and <code>Cache-Control</code> are not allowed;
1127            use <em>real</em> HTTP header fields for cache control.</p></dd>
1128        </dl>
1129      </d:desc>
1130    </d:item>
1131    
1132    <d:item name="enumerated:invalid:http-equiv:content-type"
1133        class="attribute-value-error">
1134      <d:message xml:lang="en">Character encoding declaration syntax
1135      <code class="html bad example">&lt;meta http-equiv="Content-Type" content="text/html; charset=<var>charset-name</var>"></code>
1136      is obsolete.</d:message>
1137      <d:desc xml:lang="en">
1138        <p>Old long character encoding declaration syntax
1139        <code class="html bad example">&lt;meta http-equiv="Content-Type" content="text/html; charset=<var>charset-name</var>"></code>
1140        is in use.  The document is non‐conforming.</p>
1141    
1142        <p>The new character encoding declaration syntax is:
1143          <pre class="html example"><code>&lt;meta charset="<var>charset-name</var>"></code></pre>
1144        </p>
1145      </d:desc>
1146    </d:item>
1147    
1148    <d:item name="duplicate ID"
1149        class="attribute-value-error">
1150      <d:message xml:lang="en">This identifier has already been
1151      assigned to another element.</d:message>
1152      <!-- @@ <id=a xml:id=a>? -->
1153    </d:item>
1154    
1155    <d:item name="link type:bad context"
1156        class="attribute-value-error">
1157      <d:message xml:lang="en">The link type <code><var>$0</var></code>
1158      cannot be specified for this element.</d:message>
1159      <d:desc xml:lang="en">
1160        <p>The specified link type cannot be used for the element.
1161        The document is non-conforming.</p>
1162    
1163        <p>Link types are associated with limited set of elements.
1164        They cannot be used with other elements.</p>
1165    
1166        <p>For example, link type <code>bookmark</code>
1167        can be used with <code>a</code> or <code>area</code> element,
1168        while it cannot be used with <code>link</code> element.</p>
1169      </d:desc>
1170    </d:item>
1171    
1172    <d:item name="link type:non-conforming"
1173        class="attribute-value-error">
1174      <d:message xml:lang="en">The link type <code><var>$0</var></code>
1175      is non-conforming.</d:message>
1176      <d:desc xml:lang="en">
1177        <p>The specified link type is non-conforming, and therefore
1178        the document is non-conforming.</p>
1179    
1180        <dl class="switch">
1181        <dt>Link type <code>contents</code></dt>
1182          <dd>Use link type <code>index</code>.</dd>
1183        <dt>Link type <code>copyright</code></dt>
1184          <dd>Use link type <code>license</code>.</dd>
1185        <dt>Link type <code>home</code></dt>
1186          <dd>Use link type <code>index</code>.</dd>
1187        <dt>Link type <code>previous</code></dt>
1188          <dd>Use link type <code>prev</code>.</dd>
1189        <dt>Link type <code>start</code></dt>
1190          <dd>Use link type <code>first</code>.</dd>
1191        <dt>Link type <code>toc</code> or <code>top</code></dt>
1192          <dd>Use link type <code>index</code>.</dd>
1193        </dl>
1194      </d:desc>
1195    </d:item>
1196    
1197    <d:item name="mismatched charset name" class="attribute-value-error"
1198        level="m">
1199      <d:message xml:lang="en">Character encoding name <code><var>$1</var></code>
1200      is different from document character encoding
1201      <code><var>$0</var></code>.</d:message>
1202      <d:desc xml:lang="en">
1203        <p>The specified character encoding name is different from
1204        the character encoding of the document.  The document
1205        is non‐conforming.</p>
1206      </d:desc>
1207    </d:item>
1208    
1209    <d:item name="reserved browsing context name"
1210        class="attribute-value-error">
1211      <d:message xml:lang="en">Browsing context name
1212      <code><var>{@}</var></code> is reserved.</d:message>
1213      <d:desc xml:lang="en">
1214        <p>The specified browsing context name is reserved.
1215        The document is non-conforming.</p>
1216    
1217        <p>Names of browsing contexts starting with <code>_</code>
1218        (<code>U+005F</code> <code class="charname">LOW LINE</code>)
1219        are reserved so that it must not be used.</p>
1220    
1221        <p>Old version of HTML, non-HTML markup languages, and
1222        Web browsers define or implements special reserved
1223        browsing context names <code>_blank</code>,
1224        <code>_main</code>, and <code>_replace</code>.
1225        However, they are <em>not</em> conforming attribute values.</p>
1226      </d:desc>
1227    </d:item>
1228    
1229    </section>
1230    
1231    <section id="attribute-value-warnings">
1232    <h2>Attribute Value Warnings</h2>
1233    
1234    <d:item name="link type:proposed" level="s"
1235        class="attribute-value-warning should">
1236      <d:message xml:lang="en">Link type <code><var>$0</var></code>
1237      is proposed but not accepted yet; it <em>should not</em> be
1238      used until it has been accepted.</d:message>
1239      <d:desc>
1240        <p>The link type is in the <i>proposed</i> status; it
1241        <em>should not</em> be used until it has been
1242        accepted.</p>
1243    
1244        <p><strong>Warning</strong>: The data served to the
1245        conforming checker might be out of date; it might have already
1246        been accepted or rejected.  The document might or might not be
1247        conforming depending on the status.  See WHATWG Wiki
1248        for the latest information.</p>
1249      </d:desc>
1250    </d:item>
1251    
1252    </section>
1253    
1254    <section id="table-model-errors">
1255    <h2>Table Model Errors</h2>
1256    
1257    <d:item name="table:colspan creates column with no anchored cell"
1258        class="table-model-error">
1259      <d:message xml:lang="en">This <code>colspan</code> attribute
1260      results in creating a table column that does not contain
1261      any cell anchored to it.</d:message>
1262    </d:item>
1263    
1264    <d:item name="table:no cell in last row"
1265        class="table-model-error">
1266      <d:message xml:lang="en">The table has no cell (<code>td</code> or
1267      <code>th</code>) in the last row.</d:message>
1268    </d:item>
1269    
1270    <d:item name="table:rowspan extends table"
1271        class="table-model-error">
1272      <d:message xml:lang="en">This <code>rowspan</code> attribute
1273      results in creating a table row that does not contain
1274      any cell anchored to it.</d:message>
1275      <d:desc xml:lang="en">
1276        <p>The <code>rowspan</code> attribute value of the cell
1277        is so specified that it extends a table in the row axis.
1278        However, the extended row does not contain any cell by itself.
1279        The document is non-conforming.</p>
1280    
1281        <p>For example, the table below is non-conforming:
1282          <pre class="html bad example"><code>&lt;table>
1283    &lt;tbody>
1284    &lt;tr>&lt;td rowspan=2>&lt;/td>&lt;/tr>
1285    &lt;/tbody>
1286    &lt;/table></code></pre>
1287        ... since the second row contains only
1288        a cell that spans between first and second rows.</p>
1289      </d:desc>
1290    </d:item>
1291    
1292    </section>
1293    
1294    <section id="imt-warnings">
1295    <h2>Internet Media Type Warnings</h2>
1296    
1297    <d:item name="IMT:obsolete subtype"
1298        class="should" level="s">
1299      <d:message xml:lang="en"><code><var>{@}</var></code>: An <em>obsolete</em>
1300      subtype is used.</d:message>
1301      <d:item xml:lang="en">
1302        <p>The specified Internet Media Type is registered with status
1303        of <i>OBSOLETE</i>.</p><!-- @@ SHOULD NOT? -->
1304        
1305        <dl class="swtich">
1306        <dt>Media type <code>text/ecmascript</code></dt>
1307          <dd>Media type <code>text/ecmascript</code> is obsoleted in
1308          favor of <code>application/ecmascript</code>.  Note that
1309          <code>text/javascript</code> would be better alternative
1310          for many cases.</dd>
1311        <dt>Media type <code>text/javascript</code></dt>
1312          <dd>Media type <code>text/javascript</code> is obsoleted by
1313          <abbr>IETF</abbr> with backward incompatible alternate
1314          <code>application/javascript</code> for architectural
1315          purity.<!-- @@ ref? -->  Realist may ignore this warning.</dd>
1316        </dl>
1317      </d:item>
1318    </d:item>
1319    
1320    <d:item name="IMT:private subtype"
1321        class="should" level="s">
1322      <d:message xml:lang="en"><code><var>{@}</var></code>: A private
1323      (<code>x-</code> or <code>x.</code>) subtype is used.</d:message>
1324    </d:item>
1325    
1326    <d:item name="IMT:unregistered subtype"
1327        class="should" level="s">
1328      <d:message xml:lang="en"><code><var>{@}</var></code>: The subtype is
1329      not registered to IANA.</d:message>
1330    <!-- TODO: Unknown message?? -->
1331    </d:item>
1332    
1333    </section>
1334    
1335    <section id="uri-errors">
1336    <h2>URI (or IRI) Errors</h2>
1337    
1338    <d:item name="URI::syntax error"
1339        class="must" level="m">
1340      <d:message xml:lang="en">The specified value is syntactically not an IRI
1341      reference.</d:message>
1342      <d:desc xml:lang="en">
1343        <p>The specified value does not satisfy the syntactical requirements
1344        for IRI references.  The document is non-conforming.</p>
1345    
1346        <p>Possible causes:
1347          <ul>
1348          <li>The string might contain one or more white space characters.
1349          Especially, the <code> </code> (<code>U+0020</code>
1350          <code class="charname">SPACE</code>) character cannot be
1351          used in IRI references.</li>
1352          </ul>
1353        </p>
1354      </d:desc>
1355    </d:item>
1356    
1357    </section>
1358    
1359    <section id="uri-shoulds">
1360    <h2>URI (or IRI) Should-level Errors</h2>
1361    
1362    <d:item name="URI::dot-segment"
1363        class="should" level="s">
1364      <d:message xml:lang="en">A dot-segment (<code>.</code> or
1365      <code>..</code>) occurs in an absolute reference.</d:message>
1366      <d:desc>
1367        <p>Dot-segment (<code>.</code> or <code>..</code>) should
1368        not occur in an absolute reference.</p>
1369    
1370        <p>In relative references, dot-segments are used to represent
1371        the current (<code>.</code>) or the parent (<code>..</code>)
1372        hierarchy of the path.  Though they are also allowed
1373        in absolute references, it should be resolved to the
1374        canonical form before it has been published.</p>
1375      </d:desc>
1376    </d:item>
1377    
1378    <d:item name="URI::empty path"
1379        class="should" level="s">
1380      <d:message xml:lang="en">This IRI does not end with
1381      a <code>/</code>.</d:message>
1382      <d:item xml:lang="en">
1383        <p>The IRI does not end with a <code>/</code>.  If there is an
1384        authority component in an IRI, a <code>/</code> should be present
1385        instead of empty path component.</p>
1386    
1387        <p>For example, <code>http://www.example.com<strong>/</strong></code>
1388        is preferred to <code>http://www.example.com</code>.</p>
1389      </d:item>
1390    </d:item>
1391    
1392    <d:item name="URI::lowercase hexadecimal digit"
1393        class="should" level="s">
1394      <d:message xml:lang="en">A lowercase hexadecimal digit is used
1395      in percent-encoding.</d:message>
1396      <d:desc xml:lang="en">
1397        <p>The hexadecimal digit in percent-encoding string in the IRI
1398        is in lowercase.  Though the IRI <em>is</em> conforming,
1399        it should be in uppercase.</p>
1400      </d:desc>
1401    </d:item>
1402    
1403    <d:item name="URI::percent-encoded unreserved"
1404        class="should" level="s">
1405      <d:message xml:lang="en">An unreserved character is
1406      percent-encoded.</d:message>
1407      <d:desc xml:lang="en">
1408        <p>An unreserved character is percent-encoded in the IRI.
1409        Though it <em>is</em> conforming, it should be in the
1410        decoded (or bare) form.</p>
1411      </d:desc>
1412    </d:item>
1413    
1414    <d:item name="URI::uppercase scheme name"
1415        class="should" level="s">
1416      <d:message xml:lang="en">URI scheme name is in uppercase.</d:message>
1417      <d:desc xml:lang="en">
1418        <p>The scheme part of the IRI is written in uppercase letter.</p>
1419    
1420  s:URI::empty path;should;This IRI should explicitly end with <code>/</code>.      <p>Uppercase scheme names are not required to be processed
1421  m:URI::syntax error;must;This IRI is not syntactically valid.      correctly.</p>
1422    <!-- @@
1423     RFC 3986 3.1.
1424     > Although schemes are case-
1425       insensitive, the canonical form is lowercase and documents that
1426       specify schemes must do so with lowercase letters.
1427    
1428     > An implementation ... should only produce lowercase scheme names for
1429       consistency.
1430    -->
1431      </d:desc>
1432    </d:item>
1433    
1434    </section>
1435    
1436    <section id="cache-manifest-errors">
1437    <h2>Cache Manifest Errors</h2>
1438    
1439    <d:item name="not manifest" class="must" level="m">
1440      <d:message xml:lang="en">This document is not a cache manifest.</d:message>
1441      <d:desc xml:lang="en">
1442        <p>The specified document is <em>not</em> a cache manifest.
1443        The document is non-conforming.</p>
1444    
1445        <p>An entity labeled as Internet media type
1446        <code>text/cache-manifest</code> must contain a cache manifest.</p>
1447    
1448        <p>A cache manifest must start with a line whose content is
1449        <code class="manifest example">CACHE MANIFEST</code>
1450        (exactly one space character between
1451        <code>CACHE</code> and <code>MANIFEST</code>).</p>
1452      </d:desc>
1453    </d:item>
1454    </section>
1455    
1456    <section id="information">
1457    <h2>Stability Information</h2>
1458    
1459    <d:item name="status:cr:element" class="level-i" level="i">
1460      <d:message xml:lang="en">This element is in the
1461      <strong>call for implementation</strong> stage.</d:message>
1462      <d:desc xml:lang="en">
1463        <p>The element is in the call for implementation stage.</p>
1464        
1465        <p>Usually, using the element is safe.  However, it is a new feature
1466        so that it might not be implemented correctly.  If it is found that
1467        the feature is hard or impossible to implement, the feature
1468        might be revised, or in some case it might be dropped.</p>
1469    
1470        <p>Elements defined by Atom 1.0 (IETF Proposed Standard), and XBL 2.0
1471        (W3C Candidate Recommendation) belong to this class.</p>
1472      </d:desc>
1473    </d:item>
1474    
1475    <d:item name="status:lc:element" class="level-i" level="i">
1476      <d:message xml:lang="en">This element is in the <strong>last
1477      call for comments</strong> stage.</d:message>
1478      <d:desc xml:lang="en">
1479        <p>The element is in the last call for comments stage.</p>
1480        
1481        <p>The element is relatively mature, though the standardization
1482        is not done yet.  It may be used for experiments.  Since it is a new
1483        feature, it might not be implemented correctly or at all.  If it is
1484        found that the feature is hard or impossible to implement, the feature
1485        might be revised or might be dropped.</p>
1486    
1487        <p>Elements defined by Web Forms 2.0 as well as some elements
1488        defined by HTML5 belong to this class.</p>
1489      </d:desc>
1490    </d:item>
1491    
1492    <d:item name="status:wd:element" class="level-i" level="i">
1493      <d:message xml:lang="en">This element is documented in a <strong>working
1494      draft</strong>.</d:message>
1495      <d:desc xml:lang="en">
1496        <p>The element is documented in a working or editor's draft
1497        and not yet completed.</p>
1498        
1499        <p>The element should not be used for any practical purpose.
1500        The feature might be drastically changed later or might be
1501        entirely removed.</p>
1502    
1503        <p>Most of new elements defined by HTML5 belong to this class.</p>
1504      </d:desc>
1505    </d:item>
1506    
1507    <d:item name="status:non-standard:element" class="level-i" level="i">
1508      <d:message xml:lang="en">This element is <strong>not part of any
1509      standard</strong> the conformance checker knows.</d:message>
1510      <d:desc xml:lang="en">
1511        <p>The element is not part of any standard or draft the conformance
1512        checker is aware of.</p>
1513        
1514        <p>The element should not be used for any practical purpose unless
1515        there is really a standard that defines the element.</p>
1516      </d:desc>
1517    </d:item>
1518  </section>  </section>
1519    
1520  <section id="unsupported-messages">  <section id="unsupported-messages">
1521  <h2><i>Unsupported</i> Messages</h2>  <h2><i>Unsupported</i> Messages</h2>
1522    
1523  <d:item name="unsupported:attribute"  <d:item name="element"
1524      class="unsupported">      class="unsupported" level="unsupported">
1525    <d:message xml:lang="en">This attribute is not supported by the    <d:message xml:lang="en">Conformance checking for element
1526    conformance checker; <em>it might or might not be conforming</em>.</d:message>    <code><var>{local-name}</var></code> is not supported; <em>it might or
1527      might not be conforming</em>.</d:message>
1528    <d:desc xml:lang="en">    <d:desc xml:lang="en">
1529      <p>The conformant checker does not support the attribute.      <p>The conformant checker does not support the element.
1530      It cannot determine whether the document is conforming or not.</p>      It cannot determine whether the document is conforming or not.</p>
1531    </d:desc>    </d:desc>
1532  </d:item>  </d:item>
1533    
1534  <d:item name="unsupported:element"  <d:item name="attribute"
1535      class="unsupported">      class="unsupported" level="unsupported">
1536    <d:message xml:lang="en">This element is not supported by the    <d:message xml:lang="en">Conformance checking for attribute
1537    conformance checker; <em>it might or might not be conforming</em>.</d:message>    <code><var>{local-name}</var></code> of element
1538      <code><var>{element-local-name}</var></code> is not supported;
1539      <em>it might or might not be conforming</em>.</d:message>
1540    <d:desc xml:lang="en">    <d:desc xml:lang="en">
1541      <p>The conformant checker does not support the element.      <p>The conformant checker does not support the attribute.
1542      It cannot determine whether the document is conforming or not.</p>      It cannot determine whether the document is conforming or not.</p>
1543    </d:desc>    </d:desc>
1544  </d:item>  </d:item>
1545    
1546  <d:item name="unsupported:link type"  <d:item name="link type"
1547      class="unsupported">      class="unsupported" level="unsupported">
1548    <d:message xml:lang="en">The link type <code>$0</code> is not standardized    <d:message xml:lang="en">Link type <code><var>$0</var></code> is not
1549    or registered at the time of the release of the conformance checker;    standardized or registered at the time of the release of the conformance
1550    <em>it is non-conforming unless it has now been registered</em>.</d:message>    checker; <em>it is non-conforming unless it now has been
1551      registered</em>.</d:message>
1552    <d:desc xml:lang="en">    <d:desc xml:lang="en">
1553      <p>The <code>rel</code> attribute is defined as a list of link types.      <p>The <code>rel</code> attribute is defined as a list of link types.
1554      Some common link types are defined in the HTML5 specification.      Some common link types are defined in the HTML5 specification.
# Line 214  m:URI::syntax error;must;This IRI is not Line 1560  m:URI::syntax error;must;This IRI is not
1560      The link type might have been added to the registry since then.      The link type might have been added to the registry since then.
1561      In such case it might be conforming.  Otherwise, the      In such case it might be conforming.  Otherwise, the
1562      document is non-conforming.</p>      document is non-conforming.</p>
1563    
1564        <dl>
1565        <dt>Link types <code>shortcut icon</code></dt>
1566            <dd>Link type <code>shortcut</code> is not registered.
1567            Use only <code>icon</code> for linking to so-called favicon.</dd>
1568        </dl>
1569    </d:desc>    </d:desc>
1570  </d:item>  </d:item>
1571    
1572    <d:item name="event handler"
1573        class="unsupported" level="unsupported">
1574      <d:message xml:lang="en">Conformance checking for event handler attribute
1575      is not supported; <em>it might or might not be conforming.</em></d:message>
1576    </d:item>
1577    
1578    <d:item name="media query"
1579        class="unsupported" level="unsupported">
1580      <d:message xml:lang="en">Conformance checking for media query
1581      is not supported; <em>it might or might not be conforming.</em></d:message>
1582    </d:item>
1583    
1584    <d:item name="script"
1585        class="unsupported" level="unsupported">
1586      <d:message xml:lang="en">Conformance checking for script
1587      language <code><var>$0</var></code> is not supported;
1588      <em>it might or might not be conforming.</em></d:message>
1589    </d:item>
1590    
1591    <d:item name="style"
1592        class="unsupported" level="unsupported">
1593      <d:message xml:lang="en">Conformance checking for style
1594      language <code><var>$0</var></code> is not supported;
1595      <em>it might or might not be conforming.</em></d:message>
1596    </d:item>
1597    
1598    </section>
1599    
1600    <d:catalog>
1601    manakaiCompatMode:quirks;;Quirks Mode
1602    manakaiCompatMode:limited quirks;;Limited Quirks Mode
1603    manakaiCompatMode:no quirks;;No Quirks Mode
1604    
1605    manakaiIsHTML:1;;HTML Document
1606    manakaiIsHTML:0;;XML Document
1607    </d:catalog>
1608    
1609    <section id="levels">
1610    <h2>Error Levels</h2>
1611    
1612    <table id="levels-table">
1613    <thead>
1614    <tr><th scope="col">Level</th>
1615    <th scope="col">Conforming?</th>
1616    <th scope="col">Description</th>
1617    </tr>
1618    </thead>
1619    <tbody>
1620    <tr id="level-m" class="level-m">
1621    <th scope="row"><em class="rfc2119">MUST</em>‐level error</th>
1622    <td>Non‐conforming.</td>
1623    <td>A violation to a hard requirement of the specification.
1624    The document is non‐conforming.</td>
1625    </tr>
1626    <tr id="level-s" class="level-s">
1627    <th scope="row"><em class="rfc2119">SHOULD</em>‐level error</th>
1628    <td>Non‐conforming, but <em>in some case</em>
1629    conforming.</td>
1630    <td>A violation to a requirement of the specification.
1631    The violation might be legitimize in some case.  Otherwise,
1632    the document is non‐conforming.</td>
1633    </tr>
1634    <tr id="level-w" class="level-w">
1635    <th scope="row">Warning</th>
1636    <td>Conforming.</td>
1637    <td>A warning is an advice from the conformance checker to avoid
1638    to solve a problem in a confusing or possibly wrong way.
1639    It does not affect to the conformance of the document, and
1640    may sometimes be inappropriate.</td>
1641    </tr>
1642    <tr id="level-i" class="level-i">
1643    <th scope="row">Information</th>
1644    <td>Conforming.</td>
1645    <td>An informational message just provides an additional information
1646    on the feature used in the document or the status of the retrieval
1647    or so on.
1648    It does not affect to the conformance of the document.</td>
1649    </tr>
1650    <tr id="level-u" class="level-u">
1651    <th scope="row">Not supported</th>
1652    <td><em>Unknown</em>.</td>
1653    <td>Some feature that is not supported by the conformance checker
1654    is used in the document.</td>
1655    </tr>
1656    </tbody>
1657    </table>
1658  </section>  </section>
1659    
1660  <section id="license">  <section id="license">
1661  <h2>License of This Document</h2>  <h2>License of This Document</h2>
1662    
1663  <p>Copyright 2007 <a href="http://suika.fam.cx/~wakaba/who?">Wakaba</a></p>  <p>Copyright <time>2007</time>‐<time>2008</time>
1664  <p>This library is free software; you can redistribute it  <a href="http://suika.fam.cx/~wakaba/who?" rel="author" xml:lang="ja">Wakaba</a>
1665    <code class="mail">&lt;<a href="mailto:w@suika.fam.cx">w@suika.fam.cx</a>></code>.</p>
1666    
1667    <p>This document is free software; you can redistribute it
1668  and/or modify it under the same terms as Perl itself.</p>  and/or modify it under the same terms as Perl itself.</p>
1669  </section>  </section>
1670    
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