'compilerVersion' attribute in the provider options must be 'v4.0' or later

Question

I keep getting this error when trying to debug an asp.net website (not web application):

Error 1 The value for the 'compilerVersion' attribute in the provider options must be 'v4.0' or later if you are compiling for version 4.0 or later of the .NET Framework. To compile this Web application for version 3.5 or earlier of the .NET Framework, remove the 'targetFramework' attribute from the element of the Web.config file.

All version numbers in the web.config have been set to v3.5 but I still get this error.

This happens after trying to run the site for the first time, at which point I get the unable to start debugging on web server error, followed by this one continually.

Answer 1

The IIS bindings needs setting up correctly