Facebook IPOUPDATE, 1:23 PM: Investors swapped 460M Facebook shares — the highest ever day-one trading volume for an IPO. (It beat 458M shares that traded for General Motors when it returned to the market in 2010.) But those who expected to see a big first day pop have to be disappointed. Facebook closed at $38.23, +0.7% from the offering price. Investors may have lost some enthusiasm Friday as the overall market continued to slide, at least partly due to ongoing concerns about the European debt crisis. The benchmark Standard & Poor’s 500 fell 0.74%. Still, Facebook’s IPO is estimated to have created at least 1,000 new millionaires. CEO Mark Zuckerberg told Facebook staffers to “stay focused,” Bloomberg reports. “Right now, this all seems like a big deal. Going public is an important milestone in our history,” he said. “But here’s the thing: Our mission isn’t to be a public company. Our mission is to make the world more open and connected.”

PREVIOUS, 10:05 AM: The stock price is still bouncing around but has trended up to more than $41, roughly +8% — not exciting, but better than zero. The overall market also has rebounded after initially falling on continuing concerns about the European debt crisis.

PREVIOUS, 8:58 AM: About 82M trades were made in the first 30 seconds, CNBC reports. But those who expected the stock price to soar will be disappointed: Facebook’s back to the offering price of $38 about a half-hour after the first trades, which jumped to about $42. Facebook’s opening, scheduled for 11 ET, was delayed due to a technical problem. The largest-ever Internet IPO raised $18.4B for Facebook and valued the company at about $104B. The current market prices suggest that investors consider Facebook to be a fifth as valuable as Apple (with a market cap of $499.4B), about 54% the size of Google ($203B), and a little more valuable than Amazon ($97B). It also is worth more than media giants Disney ($78.4B) and Comcast ($76.4B).

Related: Should You Buy Facebook? A Few Things To Consider Before Tomorrow’s Frenzy