ASP.NET is an excellent choice for mission critical applications. Plethora of features are added to this wonderful framework and tools like Visual studio help you cut down significant development time. Added good news is there are plenty of open source as well as commercial ASP.NET applications, in case you are looking for a ready-made solution you want to use.
Question is: which ASP.NET framework should I go with? Latest ASP.NET framework is 3.5 and have many added features than ASP.NET 2.0. Some many have the opinion that you can stick with a version that is one version down to currenty version (2.0). This way you do a close watch on bugs and solutions etc and make your decision or upgrade to 3.5
If ASP.NET is your choice for a windows Hosting Plan, be sure to follow this link to find best ASP.NET hosting options: ASP.NET Hosting