Getting error while starting .net webservice in IIS 7 on dedicated server

I made C # webservice in asp.net 2008 with 3.5 framework. I made this web service on my local machine.

Now I tried to run this web service on a dedicated client server using IIS7 (on the client server). But that gives me an error -

Could not load file or assembly 'System.Web.Extensions, Version=3.5.0.0, 
Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies.
The system cannot find the file specified.

I just added the locally published webervice and other files to IIS, and then tried to run it, but was not successful.

How can i do this?

I have no idea about this.

What are the steps to complete this task?

What changes should be made to the Web.Config file?

Please help me.

Thank.