I am wondering how do you stop people who are using IE 8 from going to Compatibility mode?
Another way to achieve this in Apache is by putting the following lines in .htaccess in the root folder of your website (or in Apache's config files).
BrowserMatch "MSIE" isIE
BrowserMatch "Trident" isIE
Header set X-UA-Compatible "IE=edge" env=isIE
This requires that you have the mod_headers and mod_setenvif modules enabled.
The extra HTTP header only gets sent to IE browsers, and none of the others.