Have you problems with understanding the ASP.NET web.config file?
Its difficult remembering the structure of the web.config file and also what each configuration section/items are available and what they mean. I often refer to previous versions of my web.config in order to understand which bits I need to add to get the desired functionality in my web app.
Here MSDN details all of the sections and the web.config file: MSDN web.config Info
