IIS on Windows 7: 400 bad request when requesting XML files
I have a website running under IIS on Windows 7. Everytime the webpage requests an XML file I receive a 400 Bad Request (diagnosed through firebug). If I request the XML file directly by typing it into my browser it works. This not only happens for .xml file extensions but .xsl too; both of which contain XML data. I found the issue. When requesting the XML files I was adding the If-Modified-Since header which is in the HTTP spec but IIS on Windows 7 seems to return 400 Bad Request when this is added. Simply removing this header from the request fixes the issue. Is your xml file static or