logging in simultaneously in two websites

I have two websites "WEBSITE 1" and "WEBSITE 2"...now i want that when someone logs in to "WEBSITE 1" he does not have to log in to "WEBSITE 2" and vice versa...ie when he/she logs in to any one of he websites a开发者_JAVA百科nd opens the other one simultaneously he/she does not have to login to the other one.

For eg: when you are logged in in gmail...you do not have to log in in youtube or orkut or google+

Probably the best and easiest way is to use cookies to store the username and session information. When the user goes to any of your websites you just have to read the cookies information to automaticaly login

Check some information here: http://msdn.microsoft.com/en-us/library/ms178194.aspx