Social networking site Facebook, started six years ago by a 20 year old student in his Harvard dorm, announced it now has 500 million users worldwide.

This number means that if Facebook were a country, it would be the third largest in the world.

"This is an important milestone for all of you who have helped spread Facebook around the world.

Now a lot more people have the opportunity to stay connected with the people they care about," Facebook's founder and CEO Mark Zukerberg said in a message on his site.

Facebook crossed the 500 million milestone yesterday.

It had over 400 million active users by February this year.

Zukerberg said in celebration of the milestone, Facebook has launched a new application called 'Facebook Stories'.

"We have put together a collection of stories you've shared with us about the impact Facebook and your friends have had on your lives," he said.

Facebook is the world's largest social networking site, surpassing Twitter which has 105 million users and LinkedIn with 70 million users.

Zukerberg started Facebook in February 2004, when he was a student at Harvard.

"Our mission at Facebook is to help make the world more open and connected. I could have never imagined all of the ways people would use Facebook when we were getting started 6 years ago," he said.

About 70 per cent of Facebook users are outside the United States. It has 12 million users in India.

An average Facebook user has 130 friends and people spend over 700 billion minutes per month on the site.

There are more than 150 million active users currently accessing Facebook through their mobile devices.

Facebook content can be translated into more than 70 languages.