Facebook boost as profits set to hit $284m Although the world's largest social networking site now has 1bn users, a milestone it reached earlier this month, concern remains over the pace at which it can convert that growth into advertising sales. Third-quarter revenues are expected to have risen 29pc to $1.23bn (£768m), when the company delivers results on Tuesday, according to analysts surveyed by Bloomberg. That is down from a 32pc rate that Facebook achieved in the second quarter. The anxiety over the pace of revenue growth has deepened because Facebook's fastest expansion is in users accessing the site on mobile devices, which command lower advertising rates. The challenge presented by mobile, which accounts for 600m of Facebook's users, was underlined last week when Google shocked Wall Street with much lower profits than forecast. Analysts blamed the growing num­bers who access the search engine on mobile devices. Mark Zuckerberg, Facebook's co-founder and chief executive, and Sheryl Sand­berg, the company's chief ope­rating officer, are stepping up their efforts to convince advertisers that they can target customers more easily on Facebook than other platforms. Over the past few months, the company has launched Face­book Exchange, which allows companies who track customers browsing their own sites to ask Facebook to serve up adverts for their products on that person's Facebook page. Facebook has struggled to win investors" backing since its $104bn flotation in May.