A Web site owner has blocked Firefox users from accessing his site in protest of a popular browser extension that blocks text and display ads.

Firefox users who go to http://jacklewis.net/weblog/ are redirected to Why Firefox is Blocked, which says the Adblock Plus extension undercuts Web sites dependant on advertising revenue.

"Accessing the content while blocking the ads therefore would be no less than stealing," wrote Danny Carlton, a Web site designer and author, who runs both sites. JackLewis.net is his personal blog site. "Millions of hard working people are being robbed of their time and effort by this type of software," he added in a posting on the Why Firefox is Blocked Web site.

The conflict underscores the dilemma facing Web sites that make money through advertising and offer free content to users. Adblock is just one of a variety of free tools, such as the Hosts file, that block the delivery of ads from servers run by ad networks.

The Hosts file can be employed to block ads for browsers such as Microsoft's Internet Explorer. Browsers can also be tweaked to block ads through modification of a CSS file, which contains rules on how content is displayed in a browser.

Carlton writes that he can't block only the Firefox users that have the extension installed, so he's blocking all Firefox users since it's "the only alternative." Carlton also posted PHP and JavaScript code that blocks Firefox users from viewing a Web page.

"The real problem is Adblock Plus's unwillingness to allow individual site owners the freedom to block people using their plug-in," Carlton wrote.

Carlton, who declined to comment for this story, is now enduring the invective of Firefox fans, which hasn't exactly been polite at times, he notes.

Adblock Plus is listed on a Mozilla Web site as the second most popular add-on for the open source browser. PC World, which is owned by IDG, named the extension one of the best 100 products of 2007.

Once installed, users can right-click on a banner ad to block it. Users can also subscribe to specific filter lists, which will block common ads delivered in certain regions. Users can also unblock ads, as well as see the full URLs for where the ads were served from.

Although Adblock is not created by Mozilla, Carlton also blames the organization, which is responsible for Firefox development.

"If you are offended by the Mozilla Corp.'s endorsement of dishonesty please contact the Mozilla Foundation and ask them to stop empowering Internet theft," Carlton wrote.

Mozilla officials had no comment on Thursday.

The creator of Adblock Plus, Wladimir Palant, wrote earlier this year that the popularity of the tool can be attributed to poor Web site design, which has overwhelmed users with too many ads.

"Why does everybody who puts up a site on the Internet assume that making users watch as many ads as possible is the best business strategy?" Palant wrote. "It isn't Mozilla who is pushing Adblock Plus into mainstream -- you [Web-site operators] are.

"As I wrote down earlier, there is only one reliable way to make sure your ads aren't blocked -- make sure the users don't want to block them," Palant wrote.