On the NASDAQ stock exchange, Facebook shares jumped more than 10% within minutes of its debut on the stock market.
Shares of Facebook rose to $ 42, initially valued at $ 38 each, before returning to trading.
Mark Zuckerberg, 28, who started Facebook while at university, opened a remote store on the Nasdaq earlier.
He appeared via video link from a celebration at the company’s headquarters in California.
There was a delay of about half an hour in the beginning of Facebook’s stock trading, which analysts say reflects the huge demand for shares.
The initial share price of $ 38 estimated the eight-year social networking site at $ 104 billion.
Strong demand had prompted the company to increase both the price and the number of shares available for sale.
Facebook owners put just under a fifth of the company’s total stock, about $ 421 million, which could raise about $ 18 billion.
The site is widely used for social updates, and although Facebook has said that its use of mobile devices is the key to new profits, analysts doubt how much space there is for advertising on such platforms.
Car giant General Motors added to those doubts, saying on Tuesday that it would no longer pay for advertising on the site.
Online strategy consultant Atul Chitnis said the question was whether Facebook had a strategy to attract advertisers.
“I believe Facebook has a strategy, they are ready with something they haven’t talked about yet.” he said.
“How effective it is, we will have to look and see.”
He also said he expects to see a “short burst” in stock prices, which rises and then “sinks” again in a few days.
Facebook’s rating means that the social networking site costs about as much as internet shopping giant Amazon and more than the value of regulars like Disney.
The initial public offering (IPO) of the shares is the third largest in US history, after financial giant Visa and General Motors.
Facebook employees were awake all night before the event, participating in a “hackathon” at the company’s headquarters in Menlo Park, California.
This is an event where programmers work on projects and come up with new ideas.
Facebook’s profits are small compared to its size – it makes about $ 5 a year for each of its 900 million users – and its plans to increase profitability are unclear.
Oliver Pursche, president of Gary Goldberg Financial Services, said before the flotation: “We are telling our investors to hold back.
“Number one, we still don’t know what the inside and balance of the company looks like, so this is a big red flag for us. We want to understand business before we tell people to invest. “
Facebook also faces privacy concerns.
In fact, a class action lawsuit was filed against the company in the United States on Friday for “improper tracking of its members’ Internet use, even after they logged out of their accounts.”
Facebook itself has previously warned of the possible impact of evolving legal protections around the world on consumer privacy, and in particular the revision of European Union privacy laws.
Other internet companies had a mixed experience when they started selling shares.
Shares of online game maker Zynga fell 5% on its first trading day in December 2011.
But shares on LinkedIn’s business network more than doubled since their debut in May last year and are still trading well above that level, while Groupon’s shares jumped 30 percent in November.
However, they have since backed down, especially after the day-to-day trading company admitted in April that it had overestimated its previous revenues and profits.
Facebook’s flotation had an immediate impact on the value of these companies, as their share prices fell at the same time as Facebook’s fall from their initial jump.
Groupon fell 5.6 percent, LinkedIn fell 1.2 percent, while shares in Zynga were suspended after falling more than 13 percent in minutes.
New shareholders on Facebook will not have much of an opinion on how the business is run.
The offered shares are “A” shares, which carry one vote per share, as is normal, but the shares of the current owners are “B” shares, which carry 10 votes each.
They will control more than 96% of the votes after the flotation, with founder Mark Zuckerberg holding just under 56% of the company’s voting rights.
Mark Zuckerberg, who owns about 25% of the company, will gain the most from Facebook’s public distribution. Co-founders Dustin Moskowitz and Eduardo Saverin will also become paper billionaires overnight, as will founder and former Napster employee Sean Parker.
US venture capital firm Accel Partners and Russia’s Internet investment group Digital Sky Technologies also have significant stakes in Facebook, while software giant Microsoft and U2 frontman Bono also have a large return on their investment in the company.