ASP.NET 4 application issue on iis 6 on windows xp 64bit

I have deployed an ASP.NET 4 application to IIS 6 on Windows XP 64bit. This application is working perfectly 开发者_如何学运维from an IE8 session launched from Visual Studio 2010 and Cassini from the same XP workstation.

However once I deploy it to IIS 6, on the same box, and open it from IE8 directly, I get all sorts of issues with control widths and layout and also some jQuery errors for my datatable control.

Now here's the really weird part if I open the same IIS 6 web site from firefox using the exact same url everything works fine.

Why would this be happening?

So you have to add a custom header and make sure that you are forcing the ie mode to be 8. X-UA-Compatible:IE=8