Facebook's stock price fell to an all-time low after it announced its first earnings report since going public.
Shares in the company fell more than 10% to hit a low of $23.84 in after-hours trading, compared to a price of $38 when it went public in May.
The social network said it made $1.058bn in revenue for the first quarter of 2012, which 45% on a year ago. In the second quarter it made $1.18bn in revenue.
Facebook made a $157m loss for the second quarter, although that was mainly due to stock compensation expenses.
Were it not for the costs arising from its troubled initial public offering, Facebook would have made $295m.
That meant Facebook just about hit its Wall Street targets - analysts had expected revenue of $1.16 billion, according to FactSet - but only just.
Some said the company had set expectations low in order to boost its share price after its IPO
The site's users were up to 955 million, with 552 million active daily visitors.
Investors were not impressed, however, and after a brief rise its shares fell to record lows.
Slowing growth in its advertising revenues, which reached $992m (up from $776m a year ago), worried some.
David Wain-Heapy, operations director for social media specialists, Best Response Social, said Facebook needed a stronger mobile strategy.
"Satisfactory numbers from the social networking giant, but nothing special. The jury is still out on whether Facebook can be sufficiently monetised to justify its insane valuation," he said.
"Facebook urgently needs to figure out how its advertisers can best monetise its user base, and that's the great unknown.
"Just how are people willing to spend money when they are socialising online? This is the billion dollar question to which nobody yet has an answer."
Analysts also pointed to weaknesses in the average revenue Facebook makes per user - $1.21 in the first quarter, down 6% over a year ago.
Others appeared spooked by the big losses suffered by partners Zyng, whose games including FarmVille are said to represent 15% of Facebook's revenue but which made a loss of $108m in the first half of 2012.
Shares in Zynga fell by about 3.6% in after-hours trading, down to $3.06 from its IPO price of $10.
Gree, another social-network gaming site based in Japan, saw its own shares fall by 9.6% in trading on the Tokyo Stock Exchange.
"Our goal is to help every person stay connected and every product they use be a great social experience," said Mark Zuckerberg, Facebook founder and CEO. "That's why we're so focused on investing in our priorities of mobile, platform and social ads to help people have these experiences with their friends."
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