As Internet Explorer 8 render web pages in a new way than previous versions of Internet Explorer there is a good chance that one or more web pages you or your users regularly visit are broken or not displaying properly in IE8. Fortunately there is a compatibility mode in IE8 that makes web pages render as though they were displayed in IE7. This action is normally a manual one and the main problem here is that very few users are aware of this compatibility mode. To alleviate problems for the end users you can control the settings and compatibility list of web sites using group policy objects.
Start the Group Policy manager and go to Computer configuration > Administrative templates > Windows Components > Internet Explorer > Compatibility view and there look for “Use Policy List of Internet Explorer 7 sites”. Add the URLs for the web sites that you want IE 8 to always render in IE7 mode.