title: What is the default namespace for HTML / HTML5?
body: <p>According to this <a href="http://www.w3.org/TR/2011/WD-html5-20110405/namespaces.html" rel="noreferrer">page</a> by some user named "w3c" the default namespace for HTML is:</p>
  
  <pre><code>http://www.w3.org/1999/xhtml
  </code></pre>
  
  <p>He's obviously wrong since xhtml was used for a failed XML based HTML4 standard. What is the correct namespace I should use? </p>
  
  <p>Background: 
  I'm writing an app that uses XML. I want to be able to save data on the XML node using namespaces. For example,</p>
  
  <pre><code>&lt;s:Button width="100" height="100" html:color="blue" color="black" /&gt; 
  </code></pre>
  
  <p>The XML parser needs a namespace for the "html" prefix to be valid. </p>