How to automatically log out of Facebook

It may have happened to you or to a friend, but the odds are good that you've seen the results of someone leaving their Facebook account unattended. Maybe embarrassing comments were posted, maybe pictures were altered -- or maybe personal info was swiped and used for nefarious purposes. Logging out of Facebook is the best way to avoid these pitfalls, but perfect vigilance is impossible for us humans. Fortunately, a Firefox add-on called
-HTTP logout 1.3
-Pop Up LogOut 0.1.3l
-Facebook Disconnect 2.1.3 and few more can take care it for us.

 Here's how it works: 

• Install Any one from the above list.
• The add-on is enabled by default. From now on, when you close the Facebook window, the add-on will log you out. 
• It will also log you out after 60 seconds of inactivity,or depending upon the add-on setting. 60 second might not be enough for you. To increase the auto-logout time, just click Firefox in the top left, then Add-ons, then Options next to Facebook Auto-Logout. Change the number in the box near the bottom. 

That's it! These are some very simple add-on that can save a lot of grief in the long run.