I've received a "Getting back onto Facebook" email. I usually receive that email from Facebook when I enter a wrong password, but I'm sure this time it wasn't me!
What should I do now to keep my account safe?
Just enable login notifications. You'll be asked for a device name whenever you login. The name will be sent to your mobile (You have to activate facebook mobile for this). And once you name a device, like "Home",it won't ask again when you login from that device! Logging in from unnamed device always asks you this question. If you don't give a name,you'll get a message like,"an unknown device logged into your account at 15:30. Please change your password if it isn't you." Similarly,you'll get the message when you name a device like,"Home logged into your account at 18:00" but you'll get it only once!
To activate it,refer this!
This message is a scam attempt—phishing to steal your login information. Don't reply to it or attempt to login from the email. If you check the message source, it's not from Facebook, but maybe from a user's email account.
It is clearly a phishing scam. I get this alert to an e-mail account that is not even in my Facebook profile.