To clear cookies, cache and history in Firefox 4 and above:

1. Open Firefox.

2. Click the Tools menu and select Clear Recent History.

 

3. Click the drop-down menu Time range to clear: and select the range of history you'd like to delete. Indicate the details you'd like to delete by checking the appropriate boxes.

 

4. Click Clear Now.

 

Your cookies, cache and history have now disappeared in Firefox.