Want an easy way to check out the status of your cache? The Cache Status add-on is the add-on you need. This tool will let you get information about your browser’s cache – via RAM and the hard drive.
Here is more about this add-on from the developers:
This add-on adds a customizable presence to your browser window’s statusbar that gives you up-to-date information on your browser’s cache usage, both RAM and the hard drive. The presence also has a right-click context menu, where you can easily clear your browser’s cache. It can also automatically clean your cache when it reaches a specified level, through its Options.
Interested in trying Cache Status? You can pick up this extension at the Firefox Add-ons website.