Facebook early share gains fade

The shares, priced at $38 on Thursday in the largest-ever initial public offering (IPO) for a technology company, jumped 12 percent to $42.55 in the opening Nasdaq trades but within minutes fell back to the offering price.

Shortly after midday, the shares were back up 4.3 percent at $39.65.

"The reaction is a bit cooler than many would have hoped," said Gerard Hoberg, an economist at the University of Maryland.

"One reason I think is because it's a very large offering," Hoberg added.

"What I think is going on is you have a lot of bullishness from retail investors, people who use FB, and there's a lot of those investors creating a lot of buying pressure... but professionals who were looking at the numbers behind Facebook had a lot more doubts, and that is cooling the issue quite a bit."

A report on the Business Insider financial blog said the price did not fall below $38 because of a large number of standing orders at the offering price.

Lou Kerner of the Social Internet Fund said the market action suggests the IPO was correctly priced.

"The bankers appear in the first few minutes to have done a pretty good job," he said.

"The company raised a ton of money, lots of early investors, employees, and founders were able to monetize shares, and it's trading up a little, so the new investors did OK."

But elsewhere in the tech world, shares of online social game maker Zynga plunged 13.3 percent and triggered a trading halt .

Shares in Zynga, which makes popular games used on Facebook and other platforms, were halted at $7.17, near where they started at the beginning of the week before a strong climb ahead of Facebook's market debut.