System.Web.Optimization and Microsoft.Web.Optimization won't load reference in vs 2012
I had the same problem with a VS2010 project I opened in VS2012. The Microsoft.AspNet.Web.Optimization package was missing so I just needed to download it using Nuget Package Manager.
You can run in the console: Install-Package Microsoft.AspNet.Web.Optimization
I know it's confusing, but you will need to Install-Package Microsoft.AspNet.Web.Optimization
Try going to the web.config in the Views folder and removing the following line:
<add namespace="System.Web.Optimization" />
That fixed it for me.