How to Make Firefox Run Faster
Method 1
Here's something for broadband people that will really speed Firefox up:
1.Type "about:config" into the address bar and hit return. Scroll down and look for the following entries:
network.http.pipelining network.http.proxy.pipelining network.http.pipelining.maxrequests
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.
2. Alter the entries as follows:
Set "network.http.pipelining" to "true"
Set "network.http.proxy.pipelining" to "true"
Set "network.http.pipelining.maxrequests" to some number like 30. This means it will make 30 requests at once.
3. Lastly right-click anywhere and select New-> Integer. Name it "nglayout.initialpaint.delay" and set its value to "0″. This value is the amount of time the browser waits before it acts on information it receives.
If you're using a broadband connection you'll load pages MUCH faster now!
Method2
First step is downloading and installingTweak Network made by Edwin Martin
Second is restarting your Firefox.
Third Go to tools 
Tweak Network settings. (There will be a warning, click ok) Click on power and then click on apply.
And you're done.
Install Tweak Network Settings
But there is still more room to add 'turbo charger' on your firefox for 'Need For Speed' Internet Geek. Just follow this step. But beware of the risk since it may breaking driving speed limit of your country.
1. Open a browser and type about:config into the address bar and press enter.
2. Right-click anywhere and the select New >> Integer.
3. Now name it "nglayout.initialpaint.delay " and set its value to "0". This value is the amount of time the browser waits before it acts on information it receives. The default value is 750 ms.
Method 3
You can slash Firefox's slow load time by compressing the DLLs and executables. There are many choices for compression but I suggest you use UPX which is free, efficient and time proven.
1. Download UPX from http://upx.sourceforge.net/#download
2. Unzip upx.exe into your Firefox installation folder which is normally C:\Program Files\Mozilla Firefox.
3. Make sure Firefox is not running then shell to a command prompt in the Firefox installation directory.
4. Type in the following command in a single line and hit return:
for %v in (*.exe *.dll components\*.dll plugins\*.dll) do upx "C:\Program Files\Mozilla Firefox\%v"
5. If on some later occasion you want to unpack the files, just type in the command above but add the decompression switch "-d" after "do upx."
Method 4
James Meyer has written an alternate trick where you can make Firefox run faster even without losing any of the cookies, bookmarks or extensions.
He says: In my experience, what slows down Firefox is usually some preference for some installed add-on.
To fix the problem, make a copy of the pref.js file in your profile, and then edit it. The prefs.js file can be edited using notepad and it is available in your Firefox profile folder:
C:\Documents and Settings\[user]\Application Data\Mozilla\Firefox\Profiles\[xxx].default
Try removing lines that are related to various add-ons, and you will at some stage remove the line/lines that are causing the problem
A method I have tried before is simply remove half of the lines, and try running Firefox with several tabs of pages with a lot of content. When you have identified the bad half, restore the original prefs.js file and remove half of that bad half and try again.
In this way, you can identify the lines that are causing the problem and won't lose all your saved preferences.