The prefix foo generally is associated with the namespace http://some/other/namespace

Your feed defines a namespace prefix which is commonly used for a different namespace. This may cause problems with some news aggregators and RSS parsers which are not fully namespace-aware.

Other common errors include differences in case, and insertion or omission of common punctuation characters at the end of the URI.

For maximum compatibility with the widest range of news aggregators and RSS parsers, you should use the standard namespace prefix for each namespace.