What ASP.NET runtime version should I choose?
The ASP.NET runtime you choose for your hosting account should match the runtime version of the .NET applications you plan to install. Both IIS 7 and IIS 6 are compatible with runtime versions 1.1, 2.0, 3.0, and 3.5. ASP.NET v4.0 is only compatible with IIS 7.
What is ASP.NET 3.5?
What should I use to develop ASP.NET 3.5 Web sites?
Why are ASP.NET runtimes 2.0, 3.0 and 3.5 grouped together?
Using ASP.NET Cryptography Services with Your Web Site
Where Can I Find More Information About ASP.NET 2.0?
Viewing or Changing Your ASP.NET Version on Windows Hosting