Force Correct content-type for XHTML Documents - Most webservers serve XHTML content as TEXT/HTML which is definitely the right way to handle XHTML documents. In case the server isn't doing that correctly, you can force it on Apache servers with your .htaccess file.
RewriteEngine On RewriteCond %{HTTP_ACCEPT} application/xhtml\+xml RewriteCond %{HTTP_ACCEPT} !application/xhtml\+xml\s*;\s*q=0 RewriteCond %{REQUEST_URI} \.html$ RewriteCond %{THE_REQUEST} HTTP/1\.1 RewriteRule .* - "[T=application/xhtml+xml; charset=ISO-8859-1]"