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Pragadheeshwari
Login Credentials in Visual Force
How to use Login Credentials in Visual Force Pages or Sites,
I dont know how to use apex component <c:sitelogin>
What are all the ways for to use login credentials in visualforce page /Sites
to use authentication in Sites you need to subscribe to the pay version of the Customer Portal.
see the documentation and cookbook (or even the default pages) for authentication examples.
Shazam!
http://wiki.developerforce.com/index.php/Authenticating_Users_on_Force.com_Sites