Facebook has been working really hard and introducing new and useful features consistently. The latest feature is a security enhancement. You can now get notified instantly if your Facebook account is accessed from an unknown location or an unknown device.
To enable this feature, first go to your Account settings tab and click Account Settings.
As you scroll down, you’ll see Account Security close to the bottom of the list. Click change on the right to show the following option.
After you click Yes and submit, you have to re-login to enable this feature. Logout and then login again. This time, after logging in, you’ll see a Register This Computer screen. Just pick a name for your computer.
If you are on a computer then check this box, otherwise you will get an email everytime you log into Facebook even from this computer.
After your regular computer is registered, go to Account Settings again, and you’ll see each device that is used to access your Facebook account. You will also get an email and a text message if someone logs into your facebook account.