Hack Facebook or any account using Firesheep (EASY)

Very recently a new Firefox Addon has been the Cause of Hijacking facebook accounts without authorization of the owner of account. As a report, the Firesheep has been downloaded more than  210000 time within 24 hours and still going very fast. As Facebook is worlds most popular Social Networking website, therefore it has been the major victim of it, 

Firesheep uses HTTP session hijacking attack