Only
 a few Facebook users are aware of this fact, but for many others, this 
might seem a bit surprising. Facebook accepts the following forms of 
your password:
1. Your Original Password
Let
 me explain this to you with the following example. Assume that your 
default Facebook password that you created during the sign-up process 
is:
2. Password with the Case Toggled
In the above password the letters ‘F’ and ‘P’ are in uppercase and the remaining are in the lowercase. If you TOGGLE the case
 where all the UPPERCASE characters are converted into the lowercase and
 vice versa, your default password “myFacebookPass” would become:
Now
 if you log in using the above toggled password, your Facebook will 
accept it and welcomes you! This is the first variation of your default 
password which is accepted by Facebook.
3. Password with the First Letter Capitalized
If
 the first character of your password is in the lowercase, you may just 
change that first letter to UPPERCASE and Facebook will again accept it 
and let you in. As in case of the above example where your default 
password is “myFacebookPass”, if you just change the first letter to UPPERCASE, your password would be “MyFacebookPass” and this should work fine as well:
Please note that this option will work only for the Mobile uers!
Why 3 Passwords?
Now,
 you all know that Facebook can be accessed using 3 different passwords.
 But you may be curious to know the actual reason behind it.
Well,
 this is definitely not because Facebook has a bug or a serious 
vulnerability. In fact, this is just an option provided by Facebook 
itself to make the sign-in process easier for the users. Here’s how:
The
 most common reason for the authentic logins to be rejected is when the 
CAPS LOCK is ON. This is where the first variation comes in 
handy. That means, when the CAPS LOCK is ON the case gets reversed 
(toggled) for your password but Facebook will accept this as well.
In
 case of mobile users, it is a common for the first letter of the 
password to get capitalized which often leads to the login failure. So, 
in order to tackle this issue, Facebook will also accept the password 
where only the first letter is capitalized.
Thus if the CAPS LOCK is accidentally enabled, the toggled password feature would still let you log in to your account!
