Microsoft JScript runtime error: '$' is undefined

Microsoft JScript runtime error: '$' is undefined

I created a branch in TFS for my web site project which is part of a solution with two web sites and a library of VB.NET functions. If I set the branched web site as my start up project I get this error:

Microsoft JScript runtime error: '$' is undefined

And nothing runs. 

If I use the original web site then I can everything fine.

Obviously something is missing but I can't find any files that are missing in my branch. Can anyone help?