Answer - There are 4 types of authentications. 1.WINDOWS AUTHENTICATION 2.FORMS AUTHENTICATION 3.PASSPORT AUTHENTICATION 4.NONE/CUSTOM AUTHENTICATION The authentication option for the ASP.NET application is specified by using the tag in the Web.config file, as shown below: other authentication options 1. WINDOWS AUTHENTICATION Schemes I. Integrated Windows authentication II. Basic and basic with SSL authentication III. Digest authentication IV. Client Certificate authentication 2. FORMS AUTHENTICATION You, as a Web application developer, are supposed to develop the Web page and authenticate the user by checking the provided user ID and password against some user database 3.PASSPORT AUTHENTICATION A centralized service provided by Microsoft, offers a single logon point for clients. Unauthenticated users are redirected to the Passport site 4 NONE/CUSTOM AUTHENTICATION: If we don’t want ASP.NET to perform any authentication, we can set the authentication mode to “none”. The reason behind this decision could be: We don’t want to authenticate our users, and our Web site is open for all to use. We want to provide our own custom authentication