ASP.NET 4.5 has not been registered on the Web server

If you've installed .NET framework 4.6, you may see this error due to a VS bug. Workarounds and resolutions here:

http://blogs.msdn.com/b/webdev/archive/2014/11/11/dialog-box-may-be-displayed-to-users-when-opening-projects-in-microsoft-visual-studio-after-installation-of-microsoft-net-framework-4-6.aspx

EDIT:

As noted in some of the comments, this can happen behind the scenes after upgrading to Windows 10 or Visual Studio 2015.

Maybe you have to execute the following in the Visual Studio Tools command prompt:

aspnet_regiis -i

You can read more about the ASP.NET IIS Registration Tool (Aspnet_regiis.exe) here.

On Windows 8.1, since .NET 4.5 is built-in, the fix is to run this from an administrative command-prompt:

dism.exe /Online /Enable-Feature /all /FeatureName:IIS-ASPNET45