acebook, the world's largest Internet social network, said Tuesday it made more money than it spent, becoming cash flow positive for the first time since it was started in a Harvard dorm room nearly six years ago. The Palo Alto, Calif., company also said it had reached 300 million active users.

The site reached 150 million users in only five years, a fast growth rate by any measure. But it atomized its own speed record this year by going from 150 to 300 million users in a little over nine months.

Propelled by that growth, Facebook became cash flow positive ahead of schedule, it said. The company had expected to hit that milestone in 2010. "This is important to us because it sets Facebook up to be a strong independent service for the long term," Chief Executive Mark Zuckerberg wrote in a blog post. Facebook, which has taken close to $600 million in financing, makes its money from advertising, including an auction system where marketers can pay to target small products and services to certain demographics. The private company does not disclose its revenues. Facebook has had a tumultuous childhood, frequently getting in hot water over the way it shares, stores and uses personal information uploaded by its users.

In August, the company announced it was starting a yearlong project to clarify and tighten its privacy controls after a Canadian government agency complained about the site's policies.

But Facebook's rapid growth is perhaps the best evidence of its utility and its general appeal to users around the world. The company says its fastest growing demographic is now people 35 and over, and in the U.S., the site's nearly 90 million visitors made it the fourth most-trafficked Web property in July, according to web ratings firm comScore. The company, which has close to 1,000 employees, was valued at $10 billion in a transaction earlier this year in which the Russian venture firm Digital Sky Technologies bought $200 million worth of its stock.