Confused about the web.config file?  The following article at dotnetjohn.com offers an excellent overview and explanation:

http://www.dotnetjohn.com/PrintFriend.aspx?articleid=24

Another very important note is the placement of the web.config file.. ASP.NET allows you to have different web.config files for different ASP.NET applications within the same site... check the following article for more clarification: Where does ASP.Net search for web.config file?