Facebook's biggest challenge and its greatest opportunity now lies in mobile devices. Most Facebook users access it using a mobile phone or tablet computer, but the company only started showing mobile ads about 9 months ago.
Facebook said it generated 23%, or $306 million, of advertising revenue from mobile, up from 14% in the third quarter.
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Junk food advertising is to be banned across all children's media - including online and social - in a bid to tackle childhood obesity.
The pilot of the private jet that crash landed killing three members of Osama bin Laden's family had a "very high workload".