As mentioned earlier, ASP.NET configuration files are XML documents. The root node of the document is always called configuration. Within the configuration node are a variety of nodes and subnodes that contain additional settings; these are grouped into section handlers.
The next few sections describe the default section handlers in the System.Web section of a Web configuration file. Because each Web.Config file ultimately inherits its settings from Machine.Config, the descriptions apply to both files.
Authentication refers to the process whereby a user is granted or denied access to the page based on security credentials.
ASP.NET supports three authentication modes:
Windows authentication ...