5. Assign Memory Cache on Firefox:

Firefox doesn't use memory cache and uses system memory by default, it is good to assign a fixed memory cache to reduce the usage of memory. Here's how you do it:

1. Open the Firefox browser.
2. Key in about:config in the address bar.
   
   
3. Key in browser.cache.memory.enable in the Filter field.
   
   
4. Ensure the value of the above item is set it true, if not, double-click on it to set it to true.
5. Right-click in the browser and select New -> Integer from the pop-up.
   
   
6. Key in, browser.cache.memory.capacity, click OK.
   
   
7. You need to enter a value here and that value depends upon the RAM your computer has.
   
   
8. if you have:
   1. 256MB RAM - Enter "4096".
   2. 512MB RAM - Enter "8192".
9. Note: If you have 128MB or less RAM then you need to upgrade your RAM.  It is not very expensive.

Important: If you want to restore to default settings then change browser.cache.memory.capacity value to -1 (minus 1).

6. Release Memory when Firefox is minimized

1. Open the Firefox browser.
2. Key about:config in the address bar.
   
   
   
3. Right-click in the browser and select New -> Boolean from the pop-up.
   
   
   
4. In the popup box enter config.trim_on_minimize. Click OK.
   
   
   
5. Select True and then click OK.
   
   
   
6. Restart Firefox.