I am thinking now how the rss applications are parsing the feeds, basically if I just want to parse XML from the feed I will use XMLReader
http://content.warframe.com/dynamic/rss.php
Based on this feed I will get exception about illegal path (this is less important), BUT I can put this link to another application (link at the bottom) and it will work...
There is w3c validator which shows many error http://validator.w3.org/feed/check.cgi?url=http%3A%2F%2Fcontent.warframe.com%2Fdynamic%2Frss.php
If this rss feed really have so many "errors", why it is working with other applications? On example when i put it into: http://feed.mikle.com/