rss feed issue

This is the error that I get when I try to validate my rss feed.
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Message

HTTP Error
Explanation

Your feed couldn’t be validated because there was a problem downloading it from the web server. You should try to diagnose this using a web browser, and make sure that the URL you supplied resolves to an accessible file.

This usually means that the URL was wrong, or that permissions on the server don’t allow us to fetch that file. The error shows the message that the server sent, which may help.
Solution

Make sure this URL can be downloaded with a browser, then try again.
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I wish this stuff was in plain english.

It seems to say there is a problem with my url. My url works fine.

So if that is NOT what it says, then what does this mean?