Ben Goodger , the Firefox Lead Engineer, posted about the Firefox “memory leak”. We had many discussion before on memory problems of Firefox and Ben explained that it was a feature and not a bug. Firefox cache up to 8 pages in memory depending on the available memory in the system, the feature could be turned off by setting browser.sessionhistory.max_total_viewers value to 0 in the about:config
What I think many people are talking about however with Firefox 1.5 is not really a memory leak at all. It is in fact a feature.
To improve performance when navigating (studies show that 39% of all page navigations are renavigations to pages visited < 10 pages ago, usually using the back button), Firefox 1.5 implements a Back-Forward cache that retains the rendered document for the last few session history entries. This can be a lot of data. It's a trade-off. What you get out of it is faster performance as you navigate the web.
