Facebook - with more than 1.2 billion users worldwide - is celebrating its 10th birthday amidst challenges of keeping its original base of young users with new innovative social networks coming to the fore.

The company was launched by Mark Zuckerberg on February 4, 2004, from Harvard University.

The site was conceived as a way to connect students, and let them build an online identity for themselves, ''Computer World'' reported.

According to the company''s own recent figures, the social networking site has since expanded to cover a large swath of the world, with more than 1.2 billion people using its site on a monthly basis.

Zuckerberg, who turns 30 in May, reflected on the 10-year milestone at an industry conference in Silicon Valley last week.

He said he never envisioned Facebook, which made him one of the wealthiest people in the world, becoming so large or influential at the start. “It didn''t even occur to me that it could be us,” Zuckerberg said.

Since then, Facebook''s site and its business, now a public company, have changed dramatically, the report said.

The company was slow to react to the important mobile market, however, last week it reported that more than half its ad revenue now comes from mobile devices, the report said.

Among the growing challenges is the soaring popularity of smartphone apps that let people share images, videos, thoughts or observations at any moment.

Social networking sites such as Pinterest, Twitter and SnapChat have sparked concerns that Facebook which set a social networking trend in motion may be losing its original teen base.

A recent Princeton University study suggested that Facebook may lose around 80 per cent of its users over the next three years, a claim which was challenged by the social networking site.

According to a recent report in iStrategyLabs, Facebook lost more than 3 million users in the age group of 13 and 17 between January 2011 and January 2014.