This feed does not validate.
In addition, interoperability with the widest range of feed readers could be improved by implementing the following recommendations.
<feed xmlns="http://www.w3.org/2005/Atom">
<div xmlns:xhtml="http://www.w3.org/1999/xhtml">
^
<div xmlns:xhtml="http://www.w3.org/1999/xhtml">
^
<?xml version="1.0" encoding="utf-8"?>
<!--
Author: Sam Ruby <rubys@intertwingly.net>
-->
<!--
Description: XHTML content declared using namespace prefixes
Expect: AvoidNamespacePrefix{prefix:xhtml}
-->
<feed xmlns="http://www.w3.org/2005/Atom">
<title>Example Feed</title>
<link href="http://example.org/"/>
<updated>2003-12-13T18:30:02Z</updated>
<author>
<name>John Doe</name>
</author>
<id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>
<entry>
<title>Atom-Powered Robots Run Amok</title>
<link href="http://example.org/2003/12/13/atom03"/>
<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
<updated>2003-12-13T18:30:02Z</updated>
<summary type="xhtml">
<div xmlns:xhtml="http://www.w3.org/1999/xhtml">
This is <xhtml:b>XHTML</xhtml:b> content.
</div>
</summary>
</entry>
</feed>