Facebook is a social network launched on February 4, 2004. It was founded by MarkZuckerberg, Dustin Moskovitz, Eduardo Saverin and Chris Hughes, a former studentof Harvard University. Initially, membership of Facebook was restricted to students of Harvard University. It was expanded to the Massachusetts Institute of Technology(MIT), Boston University, Boston College and to all Ivy League schools within twomonths. Many individual universities were added in following years. Eventually, people with e-mail for universities (for example,. Edu,. Ac.uk) around the world wereelected to join the network. On 27 February 2006, Facebook began to also accepthigh school and some businesses. Since September 11, 2006, only users with 13 years of age or older can join. Users can join in one or more networks, such as aschool, a workplace or a geographical region.
The website has more than 500 million active users, Facebook's position in the ranking of visitor traffic from Alexa, rose from 60th place to 7th place. It is still the largest site of photographs of the United States, with more than 60 million new photoseach week, surpassing even turned to photography sites like Flickr.
In 1000 Sites Top Ad Planner, which records the most accessed sites in the world,through the Google search engine, released in February 2011, Facebook appears as1st place with 590 million visitors and a global reach of 38.1 %.