Request redirect to /Account/Login?ReturnUrl=/ since MVC 3 install on server

Question

We have an internal ASP.NET Webforms application running on a Windows 2008/IIS7 server which has been running fine until we installed MVC3.

Now any requests redirect

Answer 1

Updated answer for MVC 4, heavily borrowed from this page and ASP.NET MVC issue with configuration of forms authentication section (and answered on both pages)

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