title: What's the proper way to add Facebook Connect and their xmlns to (X)HTML5?
body: <p>I'm gleaning from this question [<a href="https://stackoverflow.com/questions/599334/facebook-connect-wont-validate]">Facebook Connect Won&#39;t Validate</a> that using Facebook Connect and other facebook 'social widgets' just doesn't result in a 'valid' document. </p>
  
  <p>Concerning (X)HTML5, however, what would be the (most) appropriate doctype/header if I want to include Facebook Connect content on my pages, and be as close to 'valid' (X)HTML5 as possible?</p>