Firefox 10 for Windows and Mac OS X

1. From the Tools menu, select Clear Recent History.
2. From the drop-down menu, choose Everything and make sure Cache is checked.
3. Click Clear Now.

Firefox 3.x

1. From the Tools menu, select Clear Recent History.
2. Select the Time Range to clear from the drop-down menu (Everything is recommended).
3. Click Details to choose what history elements to clear.
4. Select only the check box for Cache.
5. Click Clear Now.
6. Exit and re-launch the browser.

FireFox 1.x-3.0

1. From the Tools menu, click Clear Private Data (or Ctrl+Shift+Del).
2. Make sure the box is checked next to each option for which you wish to clear private data (browsing history, cache, cookies, authenticated sessions).
3. Click Clear Private Data Now.

If you continue to have trouble successfully clearing the browser's cache, repeat the steps above and restart your computer.