The single best extension for Firefox, hands down is Adblock. I am surprised it isn't the number one most requested extension on the Mozilla Firefox home page. Whenever I install Firefox on a new system, the first thing I do, before all else, is download Adblock Plus and the Filterset.G updater to remove unwanted content.
I have been criticized for advocating the use of Adblock in Firefox, becuase how else would web masters and site owners continue to deliver their content for free? While the argument is solid and good, there will always be ways to keep internet content free without the use of ads.
For the most case, ads are unwelcome, annoying and unattractive. It is because of these page killers that Adblock was created in the first place. I don't know of anyone who has clicked on "shoot the duck and win a free iPod!" or "You are the 1,000,000th visitor. Click here to claim your prize!" adverts. And for those who have, I would be surprised to learn that they won anything.
Perfect case in point: I was reading about the news of the Java Studio Creator announcment being made free. I am excited, and can't wait to try it out (once it finishes downloading and I get it installed). So, during the download, I was reading various sites about the press release. I came across http://au.sys-con.com/read/150537.htm. I was quite upset to see the page sitting behind two very annoying flash content pop-ups. Luckily, using Adblock is all too easy. I blocked the two ads, as well as others on the page, by completely removing them from the source to enjoy a quicker page download. Here is the page before the surgery:
And here is the page after the surgery:
Need I say anymore?