Soon after Facebook's S-1 landed at the Securities and Exchange Commission, shares of Amsterdam-based AVG priced Wednesday night at $16 apiece, the bottom of an expected $16 to $18 range. After debuting Thursday morning, its stock price sank 16%, to $13.47, in afternoon trading. It raised $128 million in the offering.

"Everybody wants to get a first-day pop, but this is a pretty standard way things have been going for IPOs recently," said AVG chief executive J.R. Smith. "I'm not worried at all about it. This is absolutely about AVG's ability to take the next step in our evolution and drives our brand, exposure and additional cash."

By contrast, the excitement over Facebook's filing seemed to have spilled over to other Internet stocks that recently went public. Shares of Zynga Inc., for example, rose 16%, to $12.25, in afternoon trading Thursday. Facebook said in its S-1 that the San Francisco social video game producer accounted for 12% of its $3.71 billion of 2011 revenue. Zynga, on the other hand, derives about 95% of its revenue from Facebook. Zynga shares went public at $10 apiece in December.

Also getting a boost Thursday were shares of daily deal site Groupon Inc., which climbed 7%, to $23, in afternoon trading. The Chicago-based company went public in November at $20 per share. Professional networking service LinkedIn Corp. shares traded at $76.39, a 6% increase, Thursday afternoon. The company's shares went public at $45 in May.

Perhaps it is naive to expect a company such as AVG to get a Facebook lift.

AVG offers its Web security software via a "freemium" model. Users, which numbered 106 million as of September, download the software for free. It then offers these customers premium products and enhanced customer support. As of Sept. 30, AVG had 15 million subscribers to its premium service.

"We give away a product that is in most cases as good or better than the big guys'," Smith said. "Then we upsell into premium suites other products and services. It doesn't take a huge conversion to make lots of money. Our competitors can't copy our freemium model."

The company also monetizes its user base by offering them the ability to do a secure Web search that ensures the search results will not lead users to sites that will infect their computer. Search engine providers pay AVG for search queries generated by this service.

A substantial portion of AVG's revenue is generated by this secure search technology. In 2010, for example, it contracted with Yahoo! Inc. to provide the search technology; nearly 22% of its total revenue that year came from that relationship. AVG currently contracts with Google Inc. for secure searches; that contract expires in September.

The company posted total revenue of $198.1 million for the nine months ended Sept. 30, compared with $159.8 million in the first nine months of 2010. Net income for those periods was $99.7 million and $47.8 million, respectively.

The company's largest shareholder is TA AVG Luxembourg, which is owned by Boston private equity firm TA Associates Inc. The fund owns 28.1% of AVG. It acquired its stake in 2009 for $200 million.

PEF V Information Technology II holds 26.7% of the company's shares post-offering. Grisoft Holdings BV owns 15.4%, and Intel Corp.'s venture arm, Intel Capital, owns 11.9%.

AVG snagged the same lead managers as Facebook: Morgan Stanley, J.P. Morgan Chase & Co. and Goldman, Sachs & Co. Co-managing the deal were Cowen and Co. LLC, Allen & Co. LLC and JMP Securities.

For legal counsel, AVG retained Bruce Dallas and John Meade of Davis Polk & Wardwell LLP. The underwriters retained Wilson Sonsini Goodrich & Rosati PC's Aaron Alter, Tony Jeffries and Steven Bernard.

It was a mixed bag for two other companies that went public Thursday. Greenway Medical Technologies Inc., a provider of information technology and services to physicians, debuted at $10 per share after pricing below its range of $11 to $13 per share. Its stock had climbed 29%. to $12.89. in afternoon trading. Oil and gas explorer Matador Resources Co.'s shares slid 3%, to $11.65, in afternoon trading after pricing at $12 per share, well below the expected range of $14 to $16 per share.