Ok...
I'll say this last thing...
What the heck do you think the hacker well do when he gains access to your computer (I'm not saying he will because this is just a minor attack)?
Do you think you'll get a popup "Haha! I got you!"?
There's people who admitted firefox doesn't complain, and they admit they have a crappy antivirus. Does THAT make sense? I mean, who the heck is scanning your computer for virii? Firefox?
Oh come on, Firefox is a notable browser from other browsers, true, but it ain't perfect. Firefox is just a browser not a security suit.
This isn't a matter of being worried; I'm here on my sofa happily arguing with you guys on this issue with 5 browsers at hand. Did I suggest you use one of them? No! That is simply because no browser can do an anitvirus's work.
By the way, if you're happy to stay with it, then do what the heck you want. But I'll tell you one thing: Chrome, IE and Opera all complain. Firefox 3 on my computer is silently getting caching the virus in memory and cleaning it when the page refreshes. Is that good? Yes. Is that secure? No, the virus can still run.
As a web developer and with a keen interest on this subject (having devised some clever systems for attacking) I know what I'm saying about.
Looking at the code here, the virus ain't malicious. The code simply tries loading other pages in different iframes so that it can get information on how your browser sees certain things (for example what your browser sees when on gmail).
This topic should be closed, or merged with the first one.
Guys, I can't see why another one was opened. The first one had clear instructions on how to block this.
Just block the url I found (in the other topic) and block it as
KC_LC said.
Edit: DO NOT RUN ANY OF THOSE ACTIVEXThe one Aertcz mentioned is to find devices connected to your network. It is a well known exploit (well to the security people at least

).