I discovered last night that if you try to log in to facebook with an email address that is similar to one that has already logged on that computer, it will autocorrect your login information and try to log you in as the previous login. Even if you click the "Not {Username}?" button and reenter the information, it still won't let you log in as the second user.
From a user experience standpoint, it was rather irritating. Is there a reason for this that I am just not seeing?
Just to clarify, it was Facebook changing it AFTER I hit the submit button, not my web browser autofilling it. It even displayed a message saying that there was a "slight typo" or something like that in my information.