Fundamental Web Application Namespaces

System.Web	Classes and interfaces to enable browser-server communication. Includes HTTPRequest and HTTPResponse , and the HTTPServerUtility object that provides access to server-side utilities and processes. Also includes classes for cookie manipulation, file transfer, exception information, and output cache control.
System.Web.Caching	Classes for caching frequently used resources on the server.
System.Web. Configuration	Classes that are used to configure ASP.NET applications.
System.Web.Hosting	Classes for working with application domains, worker requests and interfacing with IIS.
System.Web.Mail	Classes for creating and managing SMTP e-mail messages and attachments.
System.Web.Security	Classes that implement security in ASP.NET applications.