Step 1: Click Firefox at the top of the page and select Preferences.
Step 2: Select the Privacy tab, and then select clear all current history.
From here, you can choose a setting to manage your browsing history.
Step 3: Select the time range to clear and then click the Clear Now button.
Step 4: From the Privacy tab, click Remove individual cookies and then:
Select Remove All Cookies; or
Select Remove Cookie to remove individual cookies.
Step 5: Close all pop-up windows. For best results, restart your browser.