If you think that Firefox is consuming a lot of memory than try out this. Go to the address bar on your Firefox browser and write about:config
Write down on the filter browser.cache and select browser.cache.disk.capacity. By default it’s usually set to 50000. This value could be lowered depending on how much ram you have. Try 20000 if you have between 512Mb and 1GB of Ram. If you have less than 512Mb then reduce to 10000.
You can further economize your Ram consumption when Firefox is minimized, by simply sending Firefox back to the hard disk. To this, ones more about:config; right click anywhere and select New>>Boolean. Name it config.trim_on_minimize and set it’s value to TRUE. Restart Firefox.
For Linux Users this Relative Post explains how you can use the Swap to compensate your Ram
Kabatology:Open Source, Linux: Who is Using the Ram