He and other Fortune 500 companies had better get in the know. These days practically any search for a company by name will turn up ““anti’’ Web sites created by angry customers, disgruntled ex-employees, crusading activists and a handful of kooks. A Yahoo! search under ““consumer opinion’’ found 87 matches, including pages like Down with Snapple, Macy’s is an (Alleged) Criminal Organization, WalMart Sucks.com and Packard Bell is Evil.

Griping isn’t new; it usually takes the form of a hostile letter to the editor or telling your brother-in-law about the faulty dishwasher. But now Americans can complain on the Internet–and tens of thousands of people, if not more, will be able to read their horror story, true or not. So far, the response from corporate America, which spends millions protecting its public image, ranges from denial to seek-and-destroy. As a public-relations executive wanly puts it, ““This is the next great crisis area of public relations.''

In the old days corporations worried about bad publicity kept their eyes on the print and broadcast media. Then, in 1994, the watershed of Internet-related PR fiascoes happened. A college professor noticed a flaw in Intel’s Pentium chip and posted it in a popular news-group. The company ignored it and was later forced into an embarrassing and expensive recall.

Since then, industry experts say companies are taking a more vigilant approach to the Net. Last year Mrs. Fields Cookies was the victim of a rumor that it was donating cookies to the O. J. Simpson victory party. The Utah-based cookie-maker hired eWatch to find where the rumor was spreading on the Internet and help them issue electronic denials. The rumors stopped in a few days, averting a threatened boycott. Fashion designer Tommy Hilfiger blanketed the Internet with press releases in March to combat Net rumors that he made racist comments on ““The Oprah Winfrey Show’’ and on CNN.

Nike got hit last month when a story surfaced that alleged workers had died in two Chinese shoe plants due to unsafe conditions. The tale, which Nike denies, leaped from an activist’s Web page to an Associated Press story, just two days before the annual shareholders’ meeting. In response, Nike last week launched nikeworkers.com, the official Web repository of information about the company’s labor policy. ““If you let these erroneous stories go unsubstantiated, they can transform from myth to fact in the minds of consumers,’’ says Nike spokesman Vada Manager. Intel also learned its lesson. Earlier this year another Internet user posted news of a flaw in Intel’s latest Pentium II chip. Intel, which had been combing the Net since the earlier fiasco, contacted the user and offered stopgap software.

If the threat seems clear, the recourse for companies is less obvious. Heidi Howard Tandy, an intellectual-property attorney, says online opinions probably enjoy the same legal protection given to the news media and pamphleteers. But she notes the issue hasn’t been tested in court yet. Companies can try to sue for libel, but so far the more effective weapon may be nabbing sites for trademark infringement. Although they will insist that they’re only policing unauthorized use of company logos and brand names, Kmart, Viacom, Mattel and the Fox Network have successfully intimidated Web pages out existence.

Some companies dispute the idea that rogue Web sites represent a new threat. Bell Atlantic, which inherited the stigma of Nynex’s bad customer service when it merged with the East Coast carrier, says it doesn’t need a new Internet policy–despite a domain name called nynexsucks.com. The answer, it says, is better service. ““This isn’t an Internet problem,’’ says spokesman Larry Plumb, ““it’s a customer-service problem.’’ United, for its part, is monitoring its rogue site. In the meantime, it’s doing what it always does to placate dissatisfied customers: offering the creator of the rogue Web site free travel vouchers. Sometimes old-fashion works best.