After upgrading to MVC 5 I see exclamation mark for the web project, though it works

Question

I upgraded the project to MVC 5 and now experience the problem with "exclamation mark", though it works but it is annoying to see it in the VS 2012.

I mean this sign:

Answer 1

Upgrade Visual Studio 2012 to Update 4 and install Web Tools 2013.1 for Visual Studio 2012. From the blog-

With this release of ASP.NET and Web Tools, it is now possible for developers using Visual Studio 2012 and Visual Studio 2013 to collaborate on an ASP.NET MVC 5 application. This release brings in key features such as support for ASP.NET Razor 3 editing which allows developers to use syntax highlighting and Intellisense when editing a Razor View in their MVC application

The Visual Studio 2012 Update 4 also-

[addresses] compatibility and migration/round-tripping issues between VS 2012 and VS 2013 and the various platform releases to make adoption of VS 2013 as smooth as possible

According to this blog post from Brian Harry at Microsoft.