Some intranet websites require IE to run in compatibility mode, if a web application works well why would a company ever change it? However you will run into the problem that everyone is running IE in compatibility mode and your website’s layout is broken thanks to the IE rendering like it’s January 31, 2006 (IE7 mode).
For ASP.NET applications there is a quick fix!
// force IE to use latest rendering engine Response.AppendHeader("X-UA-Compatible", "IE=edge,chrome=1");
If you are wondering about chrome=1 that is for Chrome Frame.