While sharing photos and updates with friends is a universal experience, Facebook is customized depending on where you live. In Japan, for example, users can list their blood type on their profiles, as it's something that would typically come up in conversation when you meet someone — kind of like horoscopes in the U.S.
Beyond language, another hurdle was mobile. The iPhone came along in 2007, and Facebook's iPhone app soon followed. But the app was slow and buggy, fueling concerns that it wouldn't be able to transform into a "mobile-first" company, as it wanted to be. About the time of its initial public offering of stock, potential investors fretted about its ability to make money from mobile ads.
That's no longer an issue. Facebook's stock is trading near record highs. The majority of the company's advertising revenue now comes from mobile, rather than Web ads.
No doubt other challenges will come.
"At some point there will be barriers such as illiteracy, (creating) hardware for people who can't read and write," Olivan said.
Content on the Internet will have to be translated into languages that are barely represented online today.
"That's why this is a 10-year undertaking," he said. "The entire industry has to tackle the problem."
On any given day, 81 percent of Facebook's users are outside the U.S. and Canada.
"My day is not complete without checking my Facebook account," said Syaiful Anwar, a 47-year-old restaurant owner in Pekanbaru on Indonesia's Sumatra island. "To find out what is happening in this world, to bring together my friends and relatives (is) now just a click (of a) mouse away."
Indonesia has 65 million users who log in at least once a month. That's about a quarter of the country's population. India boasts another 93 million.
As Facebook's user base started growing in emerging markets, another hurdle emerged: the high cost of smartphones and Internet access. So, in 2011, Facebook launched an app called Facebook for Every Phone. It lets people without fancy smartphones access the most popular features, such as reading status updates and sharing photos. More than 100 million people use it each month.
Facebook is the first Internet experience for many people in India and other emerging markets, said Kevin D'Souza, Facebook's growth manager in India. That means people who have never used email are signing up for Facebook, using their phone numbers instead of an email address to log in.
"Facebook addresses a universal need," D'Souza said. "Everybody around the world wants to connect with people they care about."
Last summer, Facebook launched Internet.org, aimed at getting everyone in the world online.
"When I reflect on the last 10 years, one question I ask myself is: why were we the ones to build this? We were just students. We had way fewer resources than big companies. If they had focused on this problem, they could have done it," Zuckerberg wrote Tuesday. "The only answer I can think of is: we just cared more."
As far as birthdays go, Facebook's brought out reflection, nostalgia and lots of memories.
Connie Zong, who signed up for Facebook during her sophomore year at Harvard 10 years ago, remembers when she heard that Zuckerberg was dropping out of Harvard to work on Facebook.
"I remember thinking that guy is making such a big mistake," she said. "He's giving up a really great degree at a great university, and we're never going to hear from him again."
Associated Press writer Niniek Karmini in Indonesia and AP video journalist Priya Sridhar in Chicago contributed to this story.
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