SingleSignOn Issue

Hi,

I am getting following error::

Could not load file or assembly 'System.Web.Security.SingleSignOn, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.

I am using following code in web.config file::

55
2

https://adfsweb.treyresearch.net/claimapp/


/claimapp
240

https://adfsresource.treyresearch.net/adfs/fs/federationserverservice.asmx

 I have installed MVC3 setup but still it is showing that errror. Please help me

Thanks in advance