Although I recommend using XHTML in the pages themselves , I do not yet recommend using the XHTML MIME media type, application/xhtml+xml. Instead, you should serve your pages as plain text/html. Many existing browsers, including relatively recent ones such as Internet Explorer 5.1 for Mac OS and Internet Explorer 5.2 for Mac OS X, do not recognize application/xhtml+xml. Instead of displaying the page, they attempt to download it. I am not aware of any browsers that won't accept XHTML pages identified as text/html.