Firefox memory consumption

If you are using Firefox on a regular basis on Windows, and leave Firefox open all the time, then you might find that Firefox is using up a lot of RAM, occupying a tremendous amount of memory (gone upto 500 MB in some cases). A lot of people consider this a big memory bug in Firefox, but it is actually a feature to help you browse quicker.
This €˜feature€™ is how the pages are cached in a tabbed environment. To improve performance when navigating (studies show that 40% of all page navigations are renavigations to pages visited less than 10 pages ago, usually using the back button), Firefox implements a Back-Forward cache that retains the rendered document for the last five session history entries for each tab. This is a lot of data. If you have a lot of tabs, Firefox's memory usage can climb dramatically. It'€™s a trade-off. What you get out of it is faster performance as you navigate the web. This is good when you are navigating, but this memory remains used as long as Firefox remains open, which can cause a degradation of performance of the machine. It's does not matter even if you have closed all tabs except for 1, the cache is retained, only going when Firefox is closed.
If you want to improve the performance and change this setting so a lower amount of memory is consumed, it is possible to change the configuration:
1. Type about:config in an empty Firefox window
2. Find the variable 'browser.sessionhistory.max_total_viewer'
3. Set the value to 0
4. Once you restart, memory consumption will be way reduced