title: Facebook Connect and HTML5, xmlns available?
body: <p>Facebook Connect and their "Social Widgets" documentation mention that you need to add an <code>xmlns</code> attribute to your <code>&lt;html&gt;</code> tag on the page where it will be used. </p>
  
  <p>I understand that <code>xmlns</code> is for XML Name-spacing, and have used such with XHTML before. However, with all the recent talk about HTML4 / HTML5, without having read through the entire spec, <strong>is the <code>xmlns</code> attribute compatible with valid HTML5? What about HTML4?</strong></p>
  
  <p>If I've looked over an obvious mention of this in the docs, I'm sorry... point it out?</p>
  
  <p>EDIT: 
  A couple docs references/cites: </p>
  
  <p><a href="http://developers.facebook.com/news.php?blog=1&amp;story=198" rel="nofollow noreferrer">http://developers.facebook.com/news.php?blog=1&amp;story=198</a></p>
  
  <p><a href="https://developers.facebook.com/docs/guides/web" rel="nofollow noreferrer">https://developers.facebook.com/docs/guides/web</a></p>