IE8 have 3 kinds of browser mode, but give different user agent string
IE7 mode give you Mozilla/4.0 (compatible; MSIE 7.0; ...;)
IE8 mode give you Mozilla/4.0 (compatible; MSIE 8.0; ...; Trident/4.0; ...;)
IE8 compat view mode give you Mozilla/4.0 (compatible; MSIE 7.0; ...; Trident/4.0; ...;)
Trident/4.0 is the important string to determine the real mode and version of IE8.
