FW: A low-level Look at the ASP.NET Architecture (...and IIS)

I highly recommend this article by Rick Strahl of West Wind if you are trying to debug IIS 5/6 with ASP.NET or simply wanting to learn more about how web requests are processed. 

The article covers the ASP.NET request processing pipeline from the time the request hits HTTP.SYS until Response.End within the ASP.NET framework and everything in between.   Also, this has been useful for understanding differences between IIS 5 and IIS 6.

Note: this article is also available in print in the Nov/Dec 2005 issue of CoDe Magazine.