id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
6592	IDs must begin with a letter in HTML/XHTML, but _wp_unfiltered_html_comment does not.	guillep2k	anonymous	"The comments section uses a hidden field with name _wp_unfiltered_html_comment. Although the W3C validator doesn't mark it as an error, XHTML/HTML IDs must begin with a letter (we can say even the W3C validator is not perfect!).

The HTML specification, at section 6.2 (http://www.w3.org/TR/html401/types.html#type-id), clearly states that all IDs must start with a letter. For XHTML you have to dig a little deeper: at section 4.10 (http://www.w3.org/TR/xhtml1/#h-4.10) it says ""in XHTML 1.0 the id attribute is defined to be of type ID""; then in XML specification you must follow the ID type (http://www.w3.org/TR/2000/REC-xml-20001006#id) to ""Names and Tokens"" (http://www.w3.org/TR/2000/REC-xml-20001006#NT-Name), where it says ""[5] Name ::= (Letter | '_' | ':') (NameChar?)*"", ruling out IDs starting with underscores. Therefore, I think that the _wp_unfiltered_html_comment id breaks XHTML validity. In any case, changing it ""to be 100% sure"" wouldn't hurt. ;) The affected files are only two: wp-comments-post.php:38 and comment-template.php:610 (as of version 2.5)."	defect (bug)	closed	normal		General	2.5	normal	invalid		guillep2k