Facebook stock plunges to all-time low

After posting its first earnings report since going public, Facebook shares opened at an all time low. Facebook's stock opened at an all-time low, after its first earnings report failed to ease worries over slowing sales growth and its plan for mobile advertising.Shares of Facebook (FB) tumbled nearly 15% to below $23 on Friday, 40% below the company's initial offering price from May. 

Facebook earnings matched analysts' expectations when it reported its earnings after the bell on Thursday. The company also delivered a 32% gain in second-quarter revenue, to $1.18 billion. That slightly topped forecasts.

But investors are not sure how the company will bring in more revenue from its 955 million users. In particular, investors are concerned about how Facebook will make money off its mobile platform.

As more and more users access Facebook from smartphones, the company has faced criticism for not doing enough to keep up with the swift mobile shift. The problem is that with smaller screens on mobile devices, there is less space on which Facebook can advertise.