Facebook is one of the most-used websites on the Internet, visited by millions of users each day and home to more than 500 million accounts. Facebook began as the idea of one college student, Mark Zuckerberg. Discover how he founded on of the most successful social networking sites on the Internet, how he first got Facebook growing, and how he keeps millions of people logging in day after day.

Mark gets started -- Facebook is born -- Growth -- Challenges and successes.