When IE 9 is running in Compatibility View, AEM Web page displays correctly, but when IE 9 is not running in Compatibility View, AEM Web page cannot display (returning a 406 error) or cannot display correctly.
Cause: The MIME type requested by IE 9 does not match with the MIME type specified in the Web site. For example, in Windows 2003, the default MIME type for IIS is ".* application/octet-stream"; when IE 9 is running in Compatibility View, it requested the MIME type "*/*" when visiting the Web site, so it can successfully displays the Web page, but when IE 9 is not running in Compatibility View, it requested the MIME type "text/css", while this type is not specified in the Web site, so visits to file of this type are rejected.
Solution: Add a MIME type ".css text/css" in the Web site. Detailed steps are: open the IIS Manager, right click the default Web site, select Properties from the popup menu, then click the HTTP Headers tab, and then click the MIME Types button to add a MIME type.