Yesterday I ran into the following error while setting up a MVC project for Sitecore 7.2
Method not found: ‘System.Web.WebPages.IDisplayMode System.Web.Mvc.ControllerContext.get_DisplayMode()’.
Description: An unhandled exception occurred.
Exception Details: System.MissingMethodException: Method not found: ‘System.Web.WebPages.IDisplayMode System.Web.Mvc.ControllerContext.get_DisplayMode()’.
Problem was very easily solved by removing the Microsoft.Web.Mvc.FixedDisplayModes.dll
The dll is an old legacy fix for MVC4 and it can safely be removed when working with MVC5.