In a case that both sides acknowledge has ``novel issues of national importance,'' a South Florida appellate court has endorsed a lower court ruling that people posting messages on the Internet have no right to anonymity.

``This is a major step in civilizing the Internet,'' gloated Bruce D. Fischman, who represents Erik Hvide, a former chief executive of Hvide Marine in Fort Lauderdale. He is suing ``John Does,'' who used such screen names as Justthefactsjack, for allegedly making defamatory statements about him.

``If all anonymity is removed from the Internet, we are going to end up significantly stifling conversation,'' said Christopher A. Hansen, a lawyer with the American Civic Liberties Union who helps represent the John Does in the case.

Though there are now more than 100 John Doe anonymity cases winding their way through the nation's courts, the Hvide case has been written up in newspapers from San Francisco to Boston, at least partly because the American Civic Liberties Union has picked it to make a stand about freedom on the Internet.

``They have gotten smacked down twice on this,'' Fischman gloated. ``This means people are responsible for comments they make on the Internet. In my opinion, it adds stability to the Internet.''

``This was a big deal because it would have been the first time that an appellate court would have been discussing the rights of these John Doe defendants,'' said Christopher K. Leigh, a Fort Lauderdale attorney who represents the still-anonymous defendants in the Hvide case.

Lyrissa Lidsky, a law professor at the University of Florida who had worked with the ACLU on the case, said, ``We thought this might be the case for an appellate court to set a historic precedent about the First Amendment in cyberspace.''

Leigh and the ACLU had asked the three-judge panel of the Third District Court of Appeals to overturn a May decision by Miami-Dade Circuit Court Judge Eleanor Schockett ordering Yahoo and AOL to reveal John Doe's identity. ``Give them anonymity and nothing holds them back,'' she explained. ``That's why the Ku Klux Klan wears hoods.''

In its ruling, the appellate court simply refused to review Shockett's decision.

``The Third DCA punted,'' Leigh said.

``It doesn't set a precedent outside this case,'' Lidsky said. ``They issued no written opinion.''

The case is one of many in which large corporations and top executives are suing to discover the identity of their critics on the Internet. In Hvide's case, it is alleged that the anonymous postings caused the stock price to fall and the board of directors to fire him.

``That's nonsense,'' said Hansen of the ACLU. ``The idea that a board of directors would take seriously anonymous postings on an Internet chat board -- it just doesn't make sense to me. Anybody knows you take these chat boards with a grain of salt. These are water cooler conversations.''

What happens, Hansen said, is that angry executives hire lawyers to file barebones lawsuits and then send subpoenas to websites like Yahoo, which generally reveal identities without a fight.

Leigh called this a ``very pernicious practice'' of silencing critics. ``The Internet has a great leveling effect, and some of these corporations are scared by the truth. . . . In many of these cases, they find out the identity of the John Doe and then they drop the lawsuit.''

The ACLU would like to see the courts require some evidence of genuine legal harm before a person's anonymity is broken. ``A lot of these complaints would be thrown out of court if anyone bothered to look a them,'' Hansen said.

At least a half-dozen John Doe suits involve other South Florida companies. In one, AnswerThink, a Coral Gables consulting firm, learned through a subpoena that a contract employee was posting nasty messages about the company on a Yahoo board. The company fired him shortly before he was to receive an $896,000 fee, according to allegations in court documents.

In the Hvide case, it is expected that Yahoo will reveal the identity or identities behind the screen names within a few days.

``The message from the Third District is that you don't automatically say what you think,'' said Fischman, speaking by telephone from Harvard shortly before he spoke on a panel about the subject of anonymity and the Web.

``If it violates people's rights, if it's defamatory, you have to realize you might end up in court. This is not chilling free speech, but being more responsible.''