1. Open a new tab. Type “about:config” without quotes into the address bar and hit enter/click Go.
2. Right-click anywhere, select New, then Integer.
In the dialog prompt that appears, type: browser.cache.memory.capacity
3. Click OK. Another dialog prompt will appear. This is where you decide how much memory to allocate to Firefox. This depends on how much RAM your computer has, but generally you don’t want to allocate too little (under 8MB), but if you allocate too much, you might as well not do this. A good recommended setting is 16MB. If you want 16MB, enter this value into the dialog prompt: 16384.
For Faster Browsing ( Source )
1.Type “about:config” into the address bar and hit return. Scroll down and look for the following entries:
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 (zero). This value is the amount of time the browser waits before it acts on information it receives.