The biggest bane I have had with Firefox over the past year is that it is too bloated, crashes at will and freezes the system, all this even if a single tab you have open has some problem. Google Chrome on the other hand has a feature which will not crash the browser if there is a problem with a single tab, thanks to it using a different processes for each tab.
However, it looks like Mozilla has set out to do something about the problems users have been having with the introduction of Firefox 3.6.4, which has a feature called "Crash Protection".
Crash Protection in Firefox 3.6.4 will reduce the number of crashes that users encounter while watching videos or playing games using Flash. With the new update, Firefox will run plugins as different instances through Out-of-process plugins or OOPP.
This is definitely a good move forward and hopefully Mozilla will also move towards making Firefox more memory efficient and lightweight in future builds.
Firefox 3.6.4 offers crash protection for Adobe Flash, Apple Quicktime and Microsoft Silverlight on Windows and Linux computers. Users can upgrade to Firefox 3.6.4 by choosing the "Check for Updates" option available under the Help menu.