Have a look to the website from microsoft. I just enabled the
EmulateIE7-Modus directly on the IIS which is used by Reddot CMS.
http://msdn.microsoft.com/en-gb/library/cc817572.aspx
Implementing the META Switch on IIS
Windows Internet Explorer 8 introduces document compatibility modes
that allow Web developers to tell the browser to render their pages in
the same way as older versions would. The compatibility mode can be
specified on a per-page or per-site basis.
This document describes how to implement a very common document
compatibility mode, EmulateIE7, supported by Windows Internet Explorer
8, on a per-site basis, using custom headers in Internet Information
Services (IIS).