Unknown HTML Character Entity Reference, with Custom External Subset

Note: An external subset entity referenced from this document by SYSTEM identifier declares the unknown general entity.

Test

&unknown; is rendered as

&unknown;

© is rendered as

©

The innerHTML of the list above is:

Expected Result

Conforming XHTML 1.0 User Agent

Conforming XHTML Family User Agent

The character reference (later) is treated as a COPYRIGHT SIGN.

A user agent that reads external entities will treat the entity reference (former) as a COPYRIGHT SIGN.

A user agent that does not read the external entity in which the entity declaration for the general entity unknown will render it as a sequence of nine characters: &unknown;.

Discussion

See a SuikaWiki article on entity references in XHTML documents.