ASP.NET actually supports four types of authentication: 1.Windows authentication 2.Forms authentication 3.Passport authentication 4.Anonymous access 1.Windows authentication If your application is targeted for use inside an organization, and users accessing the application have existing user accounts within the local user database of the Web server or Active Directory, you should authenticate users with Windows authentication. 2.Forms authentication By default, Form authentication is used. Form-based authentication presents the user with an HTML-based Web page that prompts the user for credentials. 3.Passport authentication You can also authenticate users using a service from Microsoft called Passport. Passport is a centralized directory of user information that Web sites can use, in exchange for a fee, to authenticate users. Users can choose to allow the Web site access to personal information stored on Passport, such as the users' addresses, ages, and interests. 4.Anonymous access You can explicitly disable authentication for your application if you know that it will be used only by anonymous users.

Validation Controls in ASP.NET An important aspect of creating ASP.NET Web pages for user input is to be able to check that the information users enter is valid. ASP.NET provides a set of validation controls that provide an easy-to-use but powerful way to check for errors and, if necessary, display messages to the user. There are six types of validation controls in ASP.NET RequiredFieldValidation Control CompareValidator Control RangeValidator Control RegularExpressionValidator Control CustomValidator Control ValidationSummary