Under Microsoft's web services model, ASP.NET (formerly ASP+) provides the controls and infrastructure needed to build Web applications. ASP.NET controls encapsulate HTML user interface widgets such as text boxes, drop-down menus, and so on.
The ASP.NET controls run (compiled) on the Web server and project their user interface onto a browser using standard HTML. The controls expose an object-oriented, event based programming model on the server.
A part of the Microsoft .NET architecture. You can find a scary example of COBOL ASP.NET code here: http://msdn.microsoft.com/library/techart/PDC_cobol.htm#pdc_cobolweb.
http://www.asp.net/ is an MS site with more about the technology. The ASP.NET sample site formerly at http://www.ibuyspy.com is now a tab off http://www.asp.net/CITE>, or can be reached at http://www.ibuyspyportal.com and http://www.ibuyspystore.com