I was perusing stackoverflow.com questions and came upon a question regarding JavaScriptSerializer that I found quite interesting.  I decided to do a quick spike in Visual Studio to find out if I can get answer for the question.  Fired up Visual Studio 2010, created a new Console Application and tried to instantiate a JavaScriptSerializer in my code, but of course, the IDE did not recognize JavaScriptSerializer since I haven't added a reference to the necessary assembly.  In trying to fix that, I launched the Add Reference dialog and chose the .NET tab and scrolled down... and guess what.... no System.Web.Extensions... hmmm...

Thinking the problem through I know System.Web.Extensions is part of .NET 4 (which was installed when I installed VS 2010), so how come it is not available in the Add Reference dialog?

After a bit more thinking I came to realize that it's probably because Console Application is targeting the .NET Framework 4 Client Profile which does not include all the web stuffs in it.  Switching the Target framework to .NET Framework 4 (Full profile) from the Project Property, Application tab, solved the problem.