The world's largest social networking site, Facebook, has announced plans for a stock market flotation. Facebook said it would seek to raise $5bn (£3.16bn, 3.8bn euros), about half the amount many analysts expected, BBC News informs.

But the initial public offering (IPO) is still expected to be the biggest sale of shares by an internet company.

Facebook, just eight years old and started by Harvard University students, now has 845 million users and made a profit of $1bn last year.

Facebook filed its intention to float with the Securities and Exchange Commission after the US stock markets closed.

The documents revealed for the first time information about the company that had previously been the subject of speculation.

This included news that Facebook's net income in 2011 rose 65% to $1bn, off revenues of $3.71bn.

It was disclosed that founder Mark Zuckerberg owns 28.4% of Facebook, and also that the network now has 845 million monthly users and 443 million daily users.

For the first time, we have some detailed insight into the finances this extraordinary company.

What the documents show is that Facebook has been growing very rapidly and very profitably. In two years, revenues - almost entirely from advertising - have increased fivefold, with profits quadrupling to exactly $1bn in 2011.

But alongside the mass of numbers, we also get a letter from Mark Zuckerberg rather different from the conventional CEO boilerplate.

Facebook, he affirms, exists to make the world more open and connected, and not just to build a company.