Request redirect to /Account/Login?ReturnUrl=%2f since MVC 3 install on server

I solved the problem by adding the following lines to the AppSettings section of my web.config file:

<add key="autoFormsAuthentication" value="false" />
<add key="enableSimpleMembership" value="false"/>

I fixed it this way

1. Go to IIS
2. Select your Project
3. Click on "Authentication"
4. Click on "Anonymous Authentication" > Edit > select "Application pool identity" instead of "Specific User".
5. Done.

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)

<appSettings>
   ...
   <add key="PreserveLoginUrl" value="true" />
</appSettings>

...

<authentication mode="Forms">
      <forms loginUrl="~/Account/LogOn" timeout="43200" /> <!--43,200 in minutes - 30 days-->
</authentication>