Facebook is finally making profit, the privately held company said.

The social networking site, which was started six years ago by a student at Harvard University, said on Tuesday that it had reached a positive cash flow for the first time and also passed the 300-million user mark.

The stratospheric growth in the site’s user base from 150 million at the start of the year, allowed the company to turn a profit earlier than the 2010 date it had previously predicted.

“This is important to us because it sets Facebook up to be a strong independent service for the long term,” said Facebook founder Mark Zuckerberg in a blog posting.

“We are succeeding at building Facebook in a sustainable way,” he wrote. “We are just getting started on our goal of connecting everyone. We face a lot of fun and important challenges that require rethinking the current systems for enabling information flow across the web.”

The company has close to 1,000 employees and has received $600 million in financing. According to recent web figures, it is the fourth most-visited website in the US.