How do I clear my cache & cookies? (Firefox)
Managing FireFox Cookies
Check out https://support.mozilla.org/en-US/kb/delete-cookies-remove-info-websites-stored for more specific on managing cache and cookies.
Deleting all cookies
To delete all cookies stored on your computer, either open the Cookies window as explained above and use the Remove All Cookies button or else do the following:
Click the History button > Select "History" from the drop-down option
Then Click on the "Clear Recent History"
Make sure to Set the Time range to clear to Everything and select "Cookies&Cache" then click "Clear Now"