Try clearing your computer's browsing history, cache etc. And try to sign in again. If this doesn't work, Facebook has a help page that covers most problems. The following two solutions are listed under, Help - Login and Password:
I received the "Incorrect Password" error message.
- Make sure that your caps lock key is turned off, then try to log in again.
- If you were unable to log in after making sure your caps lock key was off, then try resetting your password here.
- If you were unable to log in after resetting your password, followthese instructions to troubleshoot the problem. Reset your password once more here.
- If you still can’t log in, try using a different web browser.
I received the "Incorrect Email" error message.
- Make sure that you have entered your Facebook login email address correctly. Your Facebook login email address is the email you used to sign up for Facebook or any address you confirmed as a contact email on your Facebook account after you signed up.
- If you registered a username, try logging in using your username and password. A username is your personalized Facebook URL (web address) and appears in the location bar of your browser after "http://www.facebook.com/" when you view your profile. After logging in, visit the Settings tab on the Account page to locate the email address you use to log in.
- Try logging in using your mobile number and password. If you have confirmed a mobile number onto your account, you can log in with your mobile number and password. Be sure to add the country code and remove leading zeroes and symbols when you enter your mobile number.
- Try locating your account on the password reset page.
Tip: If you can’t find your account using one option, try using the other options to find your account. - If you still cannot log in, ask one of your Facebook friends to view your profile and send you the email address listed on your account.
- To do this, ask your friend to click on the "Info" tab on your Profile page and scroll down to "Contact Information."
- Once you receive this information, try logging in with that email address.