Facebook, the social networking website founded by a Harvard University sophomore in 2004, has hit 300 million users according to a blog post by founder Mark Zuckerberg.

It's a large number, but the way we think about this is that we're just getting started on our goal of connecting everyone," Zuckerberg said.

Facebook is already the third most visited website in the world, according to page-ranking service Alexa. It is easily the world's most popular social networking site, with as many users as the United States has people.

"Earlier this year, we said we expected to be cash flow positive sometime in 2010, and I'm pleased to share that we achieved this milestone last quarter. This is important to us because it sets Facebook up to be a strong independent service for the long term," Zuckerberg added.