We’ve updated the Publisher’s Guide (http://blogs.msdn.com/rssteam/articles/PublishersGuide.aspx) with how IE7 detects if a file is a feed.  If you publish feeds, make sure that your site’s feed is detected and readable in IE7.

If a user browses to a feed though the feed discovery button on the CommandBar, IE7 assumes it is a feed and applies the feed reading view.

When a user clicks on a link to a feed, IE7 uses the MIME Content-Type information to determine if it is a feed.  Here is a list of recommended MIME Content-Types:

RSS 2.0 (.91 and .92): use text/xml (recommended) or application/rss+xml
Atom 1.0: use application/atom+xml
RSS 1.0: use application/xml or text/xml

For generic Content-Types (ex: “text/xml” and “application/xml”) IE7 reads the file and looks for specific strings to determine if it is a feed.  For details, please read the Publisher’s Guide.

Let us know if there are any issues with our implementation.  For sites that follow the guidelines but are not properly detected in IE7 Beta 2 Preview, please post the site on our wiki.
 
- Jane