Firefox 1.5 and Atom 1.0 issue
I've found an odd issue when using the "Live Bookmark" feature in Firefox 1.5 to subscribe to Atom 1.0 feeds.
Below are extracts from 2 example feeds (both of which validate against RFC 4287 using feedvalidator); one uses type="html" for each entry title, the other type="xhtml" (and a child div element with xmlns attribute, as required by the RFC):
<entry>
...
<title type="html">entry one</title>
...
</entry>
<entry>
...
<title type="xhtml">
<div xmlns="http://www.w3.org/1999/xhtml">entry one</div>
</title>
...
</entry>
The latter example (using type="xhtml") is valid and works in Safari - but Firefox 1.5 does not display the entry titles in its "Live Bookmarks" feature. If you remove the child div element, the titles then appear in Firefox - but it invalidates the feed.
Upgrading to Firefox 2 fixes this issue; if you're stuck with 1.5 then RSS 2.0 would be the better feed choice.