<p>Go to about:config and right click and go to new --> boolean and set the preference name to config.trim_on_minimize and set the boolean value to true.
</p>
<p>Now go to task manager -->process tab-->and look for firefox.exe and watch the memory usage drop when you minimize. I will have the show notes on my site, <a href="http://www.i-trash.org\">www.i-trash.org</a> if you missed anything. </p>

