How to Authenticate user to use Web application

      HIHi

Forms authentication

A system by which unauthenticated requests
are redirected to an HTML form using HTTP client-side redirection. The user
provides credentials and submits the form. If the application authenticates the
request, the system issues a cookie that contains the credentials or a key for
reacquiring the identity. Subsequent requests are issued with the cookie in the
request headers; they are authenticated and authorized by an ASP.NET event
handler using whatever validation method the application developer specifies.

http://msdn.microsoft.com/en-us/library/9wff0kyh%28v=vs.71%29.aspx

·        
Passport authentication

Centralized authentication service provided
by Microsoft that offers a single logon and core profile services for member
sites.

http://msdn.microsoft.com/en-us/library/f8e50t0f%28v=vs.71%29.aspx

·    Windows authentication

ASP.NET uses Windows authentication in
conjunction with Microsoft Internet Information Services (IIS) authentication.
Authentication is performed by IIS in one of three ways: basic, digest, or
Integrated Windows Authentication. When IIS authentication is complete, ASP.NET
uses the authenticated identity to authorize access.

http://msdn.microsoft.com/en-us/library/907hb5w9%28v=vs.71%29.aspx

I think Formsauthentication is best for your requirement

http://www.c-sharpcorner.com/uploadfile/jayendra/how-to-create-formauthentication/