A Web site owner is protesting a Firefox plug-in, Adblock Plus, that blocks advertisements. He's doing it by blocking all Firefox users from his site, whether they're running Firefox or not. It's a gutsy move. As Microsoft with its Windows Genuine Advantage screw-up this weekend reminds us, nothing builds relationships with your customers quite like giving the impression you're calling them all thieves and liars.A Canadian business news site, itbusiness.ca, reports that Danny Carlton has written code into his blog site, http://jacklewis.net/weblog to redirect Firefox users to whyfirefoxisblocked.com.

Carlton is mad at Mozilla.org, the organization behind Firefox, because, he feels, the Adblock Plus extension undercuts Web sites dependent on advertising revenue.

"Software that blocks all advertisement is an infringement of the rights of web site owners and developers," he writes. "Numerous web sites exist in order to provide quality content in exchange for displaying ads. Accessing the content while blocking the ads, therefore would be no less than stealing."

Carlton even cites Judge Posner's widely reported decision in the Aimster case, which included the novel legal notion that fast-forwarding through commercials in recorded TV programs was not fair use, but the creation of an unauthorized derivative work.

All this borders on the silly - like when Jamie Kellner, then CEO of Turner Broadcasting, said in 2002 that not watching commercials, even if you're in the bathroom, is stealing.

As far as I know, nobody has ever gone to jail for fast-forwarding through a commercial. And if anything similar happens on the Web, then anybody who has ever turned on a pop-up blocker will surely go straight to jail, do not pass Go - and that would be approximately all of us.

Carlton, for his part, has cut himself off from something approaching 20 percent of his potential audience in the United States (and nearly 30 percent in Europe) - that's Firefox's market share - and I'd say he's well on his way to antagonizing the rest.