title: What are the problems associated with serving pages with Content: application/xhtml+xml
body: <p>Starting recently, some of my new web pages (XHTML 1.1) are setup to do a regex of the request header <code>Accept</code> and send the right HTTP response headers if the user agent accepts XML (Firefox and Safari do).</p>
  
  <p>IE (or any other browser that doesn't accept it) will just get the plain <code>text/html</code> content type. </p>
  
  <p>Will Google bot (or any other search bot) have any problems with this? Is there any negatives to my approach I have looked over? Would you think this header sniffer would have much effect on performance?</p>