[1] [CITE@en[Safari Dev Center: Safari HTML Reference: Supported Attributes]]
([TIME[2010-03-20 17:49:52 +09:00]] 版)
<http://developer.apple.com/safari/library/documentation/AppleApplications/Reference/SafariHTMLRef/Articles/Attributes.html#//apple_ref/doc/uid/TP40008058-keytype>