Can any one explain me how can any social networking site or other websites earn money ?

[zamerskates]

Like Yahoo, Facebook, Hotmail, etc these websites get money based on the number of registered accounts or number of times the site was opened.
From where do they get these money ? who give them and for what ?

[Scott Hunter]

Simply put its advertising. Those site's know alot about you, they can scan your email or Facebook status for keywords and then target advertisements based on that to you. They know your age, gender, relationship status etc... Personal Information sells.