Hi   !
Hope this article will show you:   'How to clear the Firefox cache' :
          http://mzl.la/18byRQJ
Good luck   !

There is also; Empty Cache Button {web link} Cache clearing made easy. One click.

As a footnote, some users follow the steps in "How to clear the Firefox cache" have reported that the cache doesn't go to zero, and they have to click the "Clear Now" button several times. A few versions ago, Firefox switched to clearing the cache in a background process to avoid locking up the user interface. If you do not see the number going down on the page, or going down far enough, you can reload the page using Ctrl+r to check progress. In a future version, hopefully the (remaining) cache size display will be updated more frequently/consistently.