Style written inside HTML comment should not be not applied: <html xmlns="http://www.w3.org/1999/xhtml"> <head> <link rel="match" href="html_style_in_comment-ref.html"/> <style type="text/css"> h4 {color: green} <!-- h4 {color: red} --> </style> </head> <body> <p> This page tests that Style written inside HTML comment is not applied</p> This test passes if the text below is <b>Green. NOT Red.</b> <h4> This is some text. </h4> </body> </html> This causes the following newly imported W3C ref-test to fail: http/tests/w3c/html/semantics/document-metadata/the-style-element/html_style_in_comment.html
<rdar://problem/22585912>
https://wiki.whatwg.org/wiki/HTML_vs._XHTML#Element-specific_parsing has some information about this.
The problem simply was the the file extension should have been .xhtml, not .html.