Facebook shares sink to new low after 2Q results

Even though the number of people who use mobile devices and tablet computers to access Facebook had been growing fast, Facebook didn't start showing ads on its mobile app until this spring. Facebook had 543 million active monthly mobile users at the end of the quarter, a 67 percent increase from a year earlier.

In a conference call with analysts Thursday, CEO Mark Zuckerberg said Facebook's mobile users are more active than those who use the personal computer version.

"On average mobile users are around 20 percent more likely to use Facebook on any given day," he said. "So mobile not only gives us the potential to connect more people with our services and also gives us the ability to provide more value and more deeply engaging experience."

Facebook said its revenue from advertising totaled $992 million, a 28 percent increase from the same quarter last year. That number accounted for 84 percent of total revenue. The company did not say what portion was from mobile advertising. The rest came from payments and other fees, money Facebook makes from Zynga games and other apps.

AP Business Writer Bree Fowler contributed to this report.