title: facebook app question: which doctype to use and should i use XFBML or iframe?
body: <p>we are looking to build a facebook application. Our plan is to build it on an HTML 5 site, but from what I have heard, if we are to use XFBML instead of iframe on HTML 5, it would not be compatible (since XFBML is pretty much an xml namespace) and there is a slight problem in firefox..There's a cross-browser trick I have seen out there, but it wont validate:</p>
  
  <pre><code>&lt;!doctype html&gt;
  &lt;html xmlns:fb="http://www.facebook.com/2008/fbml"&gt;
  </code></pre>
  
  <p>One way to validate it is to serve it as "application/xhtml+xml" but this of course wont work in IE..</p>
  
  <p>This is my first time building an fb app, and I am hoping to get any suggestion/input from other developers who have had experience developing fb app using the most recent technology such as HTML5..My other question is of course, which one would generally be preferred, XFBML or iframe? </p>
  
  <p>As always, I'd appreciate any help/explanation that would clear out my confusion. Let me know if the question is not clear enough. Thank you. </p>