Some of my friends are on facebook but when I go to the address list it says none of them are on facebook?

Question

What's with that

Answer 1

they used a different email to register their facebook account :)

email them the invitation and they can accept you through their other email account.....

another way is search their names on the search bar :)

Answer 2

I'm not sure what you mean by address list; perhaps you mean the Friend Finder? It's possible that your friends signed up for Facebook using different e-mail addresses than the ones you have. You can search for them on Facebook by name instead of e-mail.