The federal case may help shape the boundaries of online speech.

Companies routinely go after individuals when they feel people are maligning them on the Internet. And often, legal scholars say, the Web site's owners don't fight back at all.

In this dispute, North Carolina-based Alvis Coatings Inc., which supplied the siding product used in the Townsends' $16,721 project, says the couple's Web site infringes on the company's trademarks, defames its product and intentionally misleads and confuses consumers.

Alvis is seeking more than $75,000 in damages in addition to unspecified punitive damages and attorney fees.

"We could lose everything, including the house, and still be in debt," said Alan Townsend, whose house is valued at about $150,000.

Though neither side was looking for a brawl over speech rights, the lawsuit is headed that way, said Paul Levy, an attorney for Public Citizen, which agreed to help represent the Townsends.

Internet law expert Doug Isenberg of Georgia State University said the courts need to better define free-speech issues for the Internet, and this case could help.

"The right to criticize is certainly protected in general, but it is not unlimited," Isenberg said. "Some of those limits include how you can use someone else's trademark."

The complaint filed by Alvis alleges that the name of the Townsends' Web site, spraysiding.com, "is confusingly similar" to the official Alvis site, sprayonsiding.com, as well as its trademark "Spray on Siding."

Levy argues that the Townsends have the right to use the domain name they purchased.

Courts have provided greater protection to noncommercial sites, such as the Townsends', "but it is not quite so cut-and-dry to say if it is noncommercial use it's acceptable," Isenberg said.

Judges also weigh whether a person is likely to confuse the gripe site with the real one, said Wendy Seltzer, staff attorney with the Electronic Frontier Foundation, a San Francisco-based civil-liberties group. A site that bashes a product is not likely to create such confusion, she said.

Companies have threatened scores of criticism sites with trademark infringement and have lost many of the cases that have actually gone to court, Seltzer said. But most of the time, she said, the site owners simply agree to stop before a lawsuit is even filed. Thus, the boundaries of their rights are never tested.

Having this case and others like it go to court should help better define permissible conduct — and perhaps discourage companies from such threats in the future, if they know they would likely lose, Seltzer said.

The Townsends' Web site has a message board in which other customers comment. Alvis' lawsuit, filed in September in U.S. District Court in Charlotte, N.C., contends that the Townsends are responsible for posting the "false, misleading and disparaging" comments on that message board.

A federal law offers some protections to Internet providers for content that their visitors post or transmit, and courts have separately held that criticism when framed as opinion is not libelous, legal scholars say.

But like the trademark challenges, many Web site owners don't bother fighting in such cases, said Deirdre K. Mulligan, director of the law and technology clinic at the University of California-Berkeley.

Craig Hartman, Alvis' chief operations manager, said his company sued the Townsends only after months of fruitless dealings with the couple.

Hartman said the company made three "formal generous offers" to the Townsends that were rejected.

He said the lawsuit was a last resort.

The Townsends say one settlement offer from Alvis included a gag order barring them talking about the product and a demand that the couple sell their site's domain name to the company.