Here’s a nifty trick that really works. I hate ads as much as the next person does, so here’s how you can get rid of them for Facebook.
Website: Facebook.com
Browser: Firefox (v3.0.4)
OS: Windows XP
Here is where you need to be before you can begin.
Windows 95/98/ME
c:\windows\Application Data\Phoenix\Profiles\[profile-name]\[#s].slt\chrome\
Windows NT
%UserProfile%\Application Data\Phoenix\Profiles\[profile-name]\[#s].slt\chrome\
Windows 2000/XP
C:\Documents and Settings\[USER]\Application Data\Mozilla\Firefox\Profiles\default.tea\chrome\
*NIX
~/.phoenix/[profile-name]/[#s].slt/chrome/
Mac OS X
~/Library/Application Support/Firefox/Profiles/[profile-name]/chrome/
The file you need to edit is userContent.css. The file by default does not exist, so you will need to create it.
The next step is to add the line of code to make the ads disappear. Looking at the HTML code of Facebook, we can see that the ads are in the div with an id of #sidebar_ads. So, based on that, let’s specify as much as we can and use the following line to make the ads disappear:
/* kill facebook ads - provided by www.ginside.com */
div#sidebar_ads *{ display:none !important; }
Make sure to add the * in there because if you don’t have it there, it will make the entire div disappear and not just the content within the div (which will make your browsing experience a little sub-par.)
Save the file, close Firefox (and wait for it to fully close), then start up Firefox. Go to a page with ads, let’s say, a profile page (maybe mine? add Jonathan as a friend on Facebook or become a fan of Jonathan), and POOF! The ads are gone :)
Enjoy an ad-free browsing experience on Facebook.
Please do remember, this trick is specific to your install of Firefox (and profile), so if you go on another computer, the ads will be there like they normally would be.
Thanks to Lifehacker for contributing the portion of where to find the file.