I just want to take a moment to draw your attention to a useful article on ZDNET. It seems that Facebook accepts more than one version of your password. This is unusual – mostly passwords are check in a very strict manner. It is either right or wrong. This move by Facebook softens this to allow for common problems in password entry. This is great for the vast majoirty of users as most people strongly dislike strict password schemes. It does however make Facebook susceptible to security breaches based upon this conveniance.
From the ZDNET article these are the variations on your password that Facebook will accept
Your original password.
Your original password with the first letter capitalized. This is only for mobile devices, which sometimes capitalize the first character of a word.
Your original password with the case reversed, for those with a caps lock key on.