I am giving all these details because I was not getting such error when I tried to run any of my .aspx webpage that was not using JSON technology. So lets have a look over how to solve this problem.
You just have to install .NET Framework 3.5 Service Pack and that's it. You can download the .NET Framework 3.5 Service Pack 1 microsoft website using this link http://www.microsoft.com/downloads/details.aspx?FamilyID=AB99342F-5D1A-413D-8319-81DA479AB0D7&displaylang=en
If you found this link broken then go to google.com and search Download .NET Framework 3.5 Service Pack
Note:- In this example i am getting error about version 18.104.22.168 that's why i am installing .Net framework version 3.5. Check your framework version mentioned in error.
So this is the way to get rid of this Could not load file or assembly 'System.Web.Abstractions, Version=22.214.171.124, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified. nasty error.