Microsoft Knowledge Base Article 815166 contains the following summary:
This step-by-step article describes how to troubleshoot ASP.NET Web applications. ASP.NET applications run differently than earlier Web applications. Therefore, ASP.NET applications require different techniques for isolating and for resolving problems. This article describes, at a high-level, the processes that you can use to identify and to troubleshoot issues that involve ASP.NET applications. These procedures apply only to ASP.NET applications that run on a Windows 2000 system with IIS 5.0 and the .NET Framework installed.