How to Speed Up Firefox Using the About:Config Menu

Firefox's hidden advanced menu gives you several ways to tweak the way it works under the hood. Here are a set of settings to change to get it to browse faster than ever.
 

Step 1: Go to About:Config

Go to the URL bar and enter about:config. If you want to use a more "graphical interface" use a Firefox GUI config.
Step 2: Now Search and Change These Following Values:

browser.display.show_image_placeholders = false
browser.tabs.animate = false
network.prefetch-next = true
network.http.max-persistent-connections-per-server = 8
network.http.pipelining = true
ui.submenuDelay = 0
network.dns.disableIPv6 = true

Step 3: Now Right Click, Select New Then Select the Options Accordingly.

Create integer -> Name: nglayout.initialpaint.delay -> value: 0
Create integer -> Name: content.notify.backoffcount -> value: 5
Step 4: Disable Useless Extensions:

Goto tools -> Add-ons -> Extensions -> Disable all the extensions you don't use.
Step 5: Disable Useless Plugins:

Goto tools -> Add-ons -> Plugins -> Disable all the extensions you don't use. For example i disabled the following:

Google Updates
Itunes application Detector
Java platform SE update 7
Microsoft DRM
Windows Media Player Plugin
Windows Presentation Foundation

Be careful when disabling plugins as some functionality of the browser may be disabled.