Actually, Google is correct here. Despite Appendix C, there are lots of problems associated with sending XHTML as text/html; the standard reference on the issue is http://hixie.ch/advocacy/xhtml , but you'll find plenty of other pages discussing the matter. Handling the IE factor is ideally done through server-side detection of browser capabilities and serving up regular HTML as text/html to IE, while giving application/xhtml+xml XHTML to MOS browsers. Several developers, myself included, expressed a strong desire to the IE7 developers to include support for application/xhtml+xml, but they don't seem to think it's as big an issue.