Facebook gives itself a birthday face-lift

Facebook's population grew by more than 200 million people in the last year alone, to a total of 400 million users now, Zuckerberg said in the post.

For comparison, the site's current population would make it the third-largest country in the world, behind only China and India and ahead of the United States, which has about 308 million people.

Many of the changes made to Facebook on Thursday were relatively minor.

Users can more easily access Facebook applications and games, as well as a list of friends who are currently online. The search function on the site became more prominent. And Facebook's news feed is now divided into categories for "top news" and "most recent" posts from Facebook friends, a slight change from the previous arrangement, which also allowed users to sort posts by what's newest and what's most relevant to them.