There's thousands of people out there complaining about the Firefox Memory Bug. Lets get it straight. It's not a bug. It's part of the cache feature. Here are some about:config hacks to make Firefox faster and use less RAM:

Kill the amount of RAM Firefox uses for it's cache feature. Here's how to fix it:
1. type "about:config" (w/o quotes) in the browser.
2. Find browser.sessionhistory.max_total_viewer
2. set it's value to "0"

Increase the Speed in Which Firefox loads pages
1.Type "about:config" (w/o quotes) into the address bar and hit return.
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 faster now
More options for your about:config (you might have to create some of these entries by Right Click –> New– > Interger or String

network.dns.disableIPv6: set "false"
"content.notify.backoffcount": set "5"
"plugin.expose_full_path": set "true".
"ui.submenuDelay": set "0" (zero)
Kill RAM usage to 10mb when FF is minimized
This little about:config hack will drop Firefox's RAM usage down to 10 Mb when minimized

1. Open Firefox and go to the Address Bar. Type in about:config and then press Enter.
2. Right Click in the page and select New -> Boolean.
3. In the box that pops up enter config.trim_on_minimize. Press Enter.
4. Now select True and then press Enter.
5. Restart Firefox.