Differences of ASP.NET 2.0/3.0/3.5/4.0

ASP.NET 2.0
1.Improve the Reliability and Usability of WebApplication
2.Reduce the Number of Lines of Code you have to write in common scenarios
3.Offer User Features to Personalize Web Applications
4.Provide enhanced design Features to generate consistent layouts and design

-----MasterPages
-----NestedMasterPages
-----Themes and Skins
-----Membership
-----LoginControls
-----Profile Properties
-----Web Parts

As we all know, ASP.NET 3.5 has introduced with the following main new features

1) AJAX integration
2) LINQ
3) Automatic Properties
4) Lambda expressions