MVC 4 @Scripts "does not exist"

The key here is to add

 <add namespace="System.Web.Optimization" /> 

to BOTH web.config files. My scenario was that I had System.Web.Optimization reference in both project and the main/root web.config but @Scripts still didn't work properly. You need to add the namespace reference to the Views web.config file to make it work.

UPDATE:

Since the release of MVC 4 System.Web.Optimization is now obsolete. If you're starting with a blank solution you will need to install the following nuget package:

Install-Package Microsoft.AspNet.Web.Optimization

You will still need to reference System.Web.Optimization in your web.config files. For more information see this topic:

How to add reference to System.Web.Optimization for MVC-3-converted-to-4 app

As many pointed out, restart of VS could be required after the above steps to make this work.

There was one small step missing from the above, which I found on another post. After adding

<add namespace="System.Web.Optimization" />

to your ~/Views/web.config namespaces, close and re-open Visual Studio. This is what I had to do to get this working.

@Styles and @Scripts are 2 new helpers provided by System.Web.Optimization library. As the name suggests, they bundle and minify CSS and JavaScript files or resources respectively.

Try including the namespace System.Web.Optimization either by @using directive or through web.config

http://ofps.oreilly.com/titles/9781449320317/ch_ClientOptimization.html#BundlingAndMinification

UPDATE

Microsoft has moved the bundling/minification to a separate package called Microsoft.AspNet.Web.Optimization. You can download the assembly from nuget.

This post will be useful to you.