Facebook - World's No.2 web Site.
Facebook is an online social networking service. This social networking service connect the people each other. It was founded in February 2004 by Mark Zuckerberg. Users must register before using the site, after which they may create a personal profile, add other users as friends, and exchange messages, including automatic notifications when they update their profile. Additionally, users may join common-interest user groups, organized by workplace, school or college, or other characteristics, and categorize their friends into lists such as "People From Work" or "Close Friends". As of September 2012, Facebook has over one billion active users.