i am done with my forms , sign up and login forms etc. now i want to know that how to apply mechanism like "facebook" or any other site which has login facility. i mean like a user fills in his EMail id and password and then he browse through the website and his name appears somewhere at top corner until he clicks on Logout.
how to do it ? mean i tried my best for it but couldn't :(

If you are using visual studio, create a new asp.net 4 website. Look at that example. All of the built in login controls are used in that example.

If you use these controls, you have to prep your database if you plan on storing your account info in SQL. I don't have this info handy at te moment, but you can find the information on the http://asp.net site.