Active Server Pages is a server-side scripting technology developed by Microsoft.
ASP.NET is a set of technologies in the Microsoft .NET Framework for building Web applications and XML Web Services. ASP.NET pages execute on the server and generate markup such as HTML, WML or XML that is sent to a compatible browser.
You can easily switch between versions of ASP.NET that you want to run on your website between ASP.NET 1.1, 2.0, 3.5, 4.0 & 4.5 through the online control panel. This is done on a per domain basis so you can run separate websites on different versions of ASP.NET.