We all know that  2 G-mail/Google accounts can be used in a single browser at a time, but how many of us know that the same can be done with FB account.. really very few..
 Give a try,  it's very simple.

 All you have to do is open 2 tabs, one with "www.facebook.com" and another with "www.v6.facebook.com" enter two different user accounts and see the result for your self..

 Here is a demo video for you..!