Website blocks Firefox users due to Ad Blocker

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Website blocks Firefox users due to Ad Blocker

Firefox BlockedAccording to InfoWorld, a blogger is blocking Firefox users from visiting his site in protest of the 2nd most popular Firefox plugin called AdBlock Plus, which strips banner advertisements from websites. His rationale is that when you use an advertisement blocker you are stealing.

According to InfoWorld, he stated, "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. 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.

When you go to using Firefox you are redirected to I figured he was blocking Firefox simply by the user agent string, which tells the remote web server which browser you are using. Knowing there are several popular plugins to change your Firefox user agent quickly on the fly, I figured this guy must be an idiot for trying to block Firefox users.

I changed my user agent in Firefox to Internet Explorer 7.0's user agent and went back to his page. I was still redirected to the page. Hmmmm. Interesting - he's not detecting user agent strings to block Firefox. That is the most common way to block a specific browser.

Curious, I did some more digging. I talked with Vahid Hashemian, TMC's webmaster and developer about this.  We looked at the HTML source code and Vahid immediately saw the problem. In his HTML he has this code:

Internet Explorer and even Opera returns a value for document.all, however Firefox does not. Since the '!' means "not" and Firefox does "not" return a value, it redirects the browser to So then Vahid and I got to thinking. How could we get past this code? I knew there were plenty of plugins that let you block certain strings of HTML code. So in theory, you could replace this string of HTML with "null". Greasemonkey is one of the most popular Firefox plugins that is very extensible. Using some simple Javascript code in Greasemonkey you can easily strip out this code.

You may wonder why I would go through all that trouble just to access someone's website using Firefox. I guess you could say it's part ego and part fun. He tried to stop me from doing something, so human nature is to find ways around it. It's the challenge of it all. Well, I'm off to read Jack's blog using Firefox - minus all the banner ads. Ahhh, such sweet satisfaction!

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