With Firefox 15 (due for release later today), the Firefox developers have made great strides in addressing issues that have caused the browser to consume so much memory. Ironically, what has made Firefox so great, the add-ons are the main coluprit behind these memory leaks.
he most common cause of these leaks is when an add-on accidentally holds on to extra copies of a web site in memory after our user has closed the tab. These pages pile up, and can eat massive amounts of memory for no user benefit. They leak.
In the newest Firefox release, we developed a mechanism to prevent this form of leak from happening in the first place. Firefox will now detect this pattern, recapture the leaked memory, and free it up. This means that Firefox stays responsive and stable even if an add-on is making this mistake.