title: HTML5 tags in .xhtml extension file
body: <p>I have a bunch of xhtml files with content like:</p>
  
  <pre><code>&lt;?xml version='1.0' encoding='UTF-8' ?&gt;
  &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
  &lt;html xmlns="http://www.w3.org/1999/xhtml"
        xmlns:h="http://xmlns.jcp.org/jsf/html"&gt;
  
  &lt;/html&gt;
  </code></pre>
  
  <p>I am planning to use HTML5.</p>
  
  <p>1) Can HTML5 content be saved in a .xhtml file without any issues with specific browsers? Its not the question of just changing the file extensions. The server runtime we are using, does special processing for .xhtml files. If we change the extension to html, the server runtime will try to process all plain html files too.</p>
  
  <p>2) Is following acceptable in HTML5?</p>
  
  <pre><code>&lt;?xml version='1.0' encoding='UTF-8' ?&gt;
  &lt;!DOCTYPE html &gt;
  &lt;html xmlns="http://www.w3.org/1999/xhtml"
        xmlns:h="http://xmlns.jcp.org/jsf/html"&gt;
  
  &lt;/html&gt;
  </code></pre>
  
  <p>(that is, HTML5 doctype and xml namespaces)</p>