If you are using the .NET Rss20FeedFormatter and SyndicationFeed classes to generate an RSS feed, you may run into an issue of needing to include a link attribute to the channel element. If you validate the default RSS generated the validation will fail since the channel element does not contain a link attribute.
You can test this by going to http://beta.feedvalidator.org and entering your feed Url. If you recieve the error
SyndicationFeed syndicationFeed = new SyndicationFeed(synicationItems);
syndicationFeed.AttributeExtensions.Add(new XmlQualifiedName("link"), "http://yoursite.com");
This will produce a valid RSS feed with a channel that contains a link attribute.