firefox not display rss feed with interface

Firefox displays an interface for RSS instead of the XML of the feed. For example goto: http://www.alistapart.com/site/rss

For some reason this feed is showing the XML in Firefox instead of the interface: http://www.mmpa.net/feeds/upcoming-events.rss

The xml and Content-Type heade开发者_JS百科rs are the same. Anyone see what I am missing? What's the difference?

Thanks

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Figured it out!

Firefox doesn't handle the RSS feed correctly if its compressed. (It seems, that is what my tests show but I haven't found anyone taking about it.)

Our apache installation is configured to gzip responses. One of the headers was:

Content-Encoding: gzip

I turned off apache module and it now works!

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The Content Type of the first is application/xhtml+xml while the Content Type of the second is just text/xml. As far as I can see all other feeds I have registered use Content Type application/xhtml+xml.