ATOM allows XHTML to be embedded where "content" is allowed.

Any place a 'type' attribute is allow you may have the following values:

• text - text only content:

  <atom:title type="text">I'm text</atom:title>

• html - escaped HTML:

  <atom:title type="html">&lt;b>I'm text&lt;/b></atom:title>

• xhtml - a single XHTML div element is allowed. It must be in the XHTML namespace:

  <atom:title type="xhtml">
  <div xmlns="http://www.w3.org/1999/xhtml">
  <p>A Title</p>
  <p>A Subtitle</p>
  </div>
  </atom:title>

Any other element without the type attribute that has text content is assumed to be of type 'text'.

You can use any namespace/prefix scheme you want as long as the 'div' element is in the XHTML namespace.