A Web designer who claims that Firefox's AdBlock Plus utility encourages online behavior that's tantamount to content theft is calling for a boycott of the popular Internet browser.

"I'm standing up for something I believe is right," said Danny Carlton, who has launched a Web site called WhyFirefoxIsBlocked.com.

Carlton, who is based in Oklahoma, said AdBlock Plus deprives online publishers of legitimate revenue and allows users to steal content on the sly. "AdBlock Plus does not allow me to detect it, so it's denying me control over my Web sites," said Carlton.

AdBlock was originally authored by German programmer Wladimir Palant as an open source project. It prevents banner and text ads from loading on Web pages. Carlton said the software is tacitly supported and endorsed by the Mozilla Foundation, which oversees Firefox development.

"Mozilla is endorsing the forced stealing of my resources," Carlton said in a telephone interview Wednesday. Mozilla makes AdBlock Plus available as a free download from its Web site.

Carlton said AdBlock Plus can't easily be blocked individually by Web publishers, so he's calling on them to block all Internet users arriving at their sites through the Firefox browser until Mozilla stops supporting the utility.

The issue recalls the debate over whether it's immoral for TiVo users to fast forward through network commercials, though Carlton said the cases aren't entirely similar. "TiVo doesn't force you to fast forward if you don't want to," he said, noting that AdBlock Plus' only function is to block ads.

Proponents of AdBlock Plus say Web surfers should be able to do as they please when browsing online. "When I go to a Web site, I am not engaging in any sort of bargain with the Web master," said one poster on the popular Slashdot technology blog, which is widely read by open source software users.

The issue is stirring up passions in the free software community. Carlton said he was forced to register his protest site through a third-party proxy service after he began receiving angry e-mails and phone calls from AdBlock users who found his personal details in the Internet's 'Who Is' database.

"That's not something that's going to make me back down from what I believe in," said Carlton.

Carlton said he is not receiving any technical or financial support from online publishers that may lose revenue if AdBlock Plus gains widespread use. "I'm doing this entirely on my own," he said.