Your Facebook Account Has Two Passwords

Yes! Your Facebook account has 2 passwords. One is your original password and another is original password with CASE reversed.

For example if your Facebook password is "qWerty" then you can login with another password "QwERTY"
i.e. your original password with case reversed.
After reading an article in ZDnet news I have tried this on my Facebook account and its working. In fact this is not a loophole in Facebook but a feature by the Facebook design team.
Facebook has noticed that a lot of people facing trouble while logging into their Facebook account because of CAPS-LOCK key. So Facebook introduced this multiple password feature so that a user can log in to his account even CAPS-LOCK is on.