Telerik not working

Question

Hi

I am new in web development.

I used telerik control in my project.

actually work on project which is develop in VS 10 and MVC 2

now i open that Project in VS 12 and MVC 4. I have done related 

changes in Web.Config file.

 

but now i get an error in master page like

"Value cannot be null. Parameter name: item"

in this code

<%= Html.Telerik().StyleSheetRegistrar()
.DefaultGroup(group => group.Add("telerik.common.css")
.Add("telerik.vista.css")
)
%> 

I search out in google but i dont understand what actually  error says.

Please help me to solve out this error. 

 

Thanks in advance.