This works for anyone running Firefox, not just for Ubuntu users.
Access FireFox's Configuration File type
about:config into the url

The red box is the url, where you type about:config
The Blue box is the filter box, it allows you to search through the about:config file and is where you type the blue text commands
Now let's get Firefox to run faster:Normally the browser will make one request to a web page at a time. When you enable pipelining it will make several at once, which really speeds up page loading.
Set "network.http.pipelining" to "true"
Set "network.http.proxy.pipelining" to "true"
Set "network.http.pipelining.maxrequests" to 15.
Right-click anywhereinside the firefox winodw and select New-> Integer.
Name it "nglayout.initialpaint.delay" and set its value to "0″.
Firefox downloads webpages from links it thinks you may click. This may make the "experience" seem faster but really it just bogs down Firefox and you PC.
Set "network.prefetch-next" to false
Remove some annoying Firefox features:
Turn off chrome tooltips, this causes little pop up winodws to tell you what your mouse is hovering over. If you been using Firefox for as long or longer than I have (before 1.0) you really don't need to be told what the back button does. It also hinders dragging a bookmark into the bookmark toolbar folder, the tool tip gets in the way and prevents the drop from working.
Set "browser.chrome.toolbar_tip" to false
Customize backspace button, the Ubuntu default is set to scroll up when hit. I prefer it to work like it did in Windows and go back in my page history.
Set "browser.backspace_action" to either 0 or 1
0 - Pressing backspace button will go back a page in the session history
1 - Pressing backspace button will scroll up a page in the current document and
[Shift]+[Backspace] will scroll down.
Remove URL GO button. No one over the age of 4 and under the ago of 50 uses it.
Set " browser.urlbar.hideGoButton" to true
Some of my favorite plugins:Tab Mix PlusTab Mix Plus enhances Firefox's tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager with crash recovery that can save and restore combinations of opened tabs and windows.
Foxmarks BookmarksIf you use Firefox on more than one computer, you'll want Foxmarks. Install Foxmarks on each computer, and it will work silently in the background to keep your bookmarks synchronized. As a bonus, log in to my.foxmarks.com from any computer anywhere to access your bookmarks.
Mouse GesturesAllows you to execute common commands (like page forward/backward, close tab, new tab) by mouse gestures drawn over the current webpage, without reaching for the toolbar or the keyboard.
You can also use click-only "rocker" gestures which are even faster than drawn gestures.
FlashblockFlashblock is an extension for the Mozilla, Firefox, and Netscape browsers that takes a pessimistic approach to dealing with Macromedia Flash content on a webpage and blocks ALL Flash content from loading. It then leaves placeholders on the webpage that allow you to click to download and then view the Flash content.
Adblock PlusRight-click on a banner and choose "Adblock" from the context menu - the banner won't be downloaded again. Maybe even replace parts of the banner address with star symbols to block similar banners as well. Or you select a filter subscription when Adblock Plus starts up the first time, then even this simple task will usually be unnecessary: the filter subscription will block most advertisements fully automatically.
Adblock Filterset.G UpdaterThis is a companion extension to Adblock or Adblock Plus and should be used in conjunction with it. This extension automatically downloads the latest version of Filterset.G every 4-7 days. Filterset.G is an excellent set of filters maintained by G for Adblock that blocks most ads on the internet. In addition, this extension allows you to define your own set of filters that you can add along with Filterset.G during an update. To report missed ads or problems with the extension visit the support forums http://forum.pierceive.com/.
Winestripe ThemeThis is the classic Firefox 1.5 theme for Firefox 2.0. I can't stand the default theme for Firefox 2.0, so I'm glad Florian Schmitz made this.
To enable autoscrolling & smooth scrolling go to Edit->Preferences and click Advanced. It allows you to middle click/touch pad scroll smoothly left, right, up and down web pages. It's enabled in Windows but not in Ubuntu.

edited by pHreaksYcle