OK, I understand what the messages means, but I\'m really not sure what\'s causing it. I\'m using Safari and the Web Inspector on Mac OS X, by the way.
You need to use a tool to view the HTTP headers sent with the file, something like LiveHTTPHeaders or HTTPFox are what I use. If the files are sent from the webserver without a MIME type, or with a default MIME type like text/plain, that might be what this error is about.