By default, Firefox saves all your data including browsing history, cookies, cache and even searched keywords. Although it’s fairly simple to delete your cookies and temporary files manually, Firefox has a groovy feature to automatically delete everything each time you exit Firefox. If you’re using a shared computer at school, work or home — that’s a good thing. Here’s how you configure it.
Open Firefox, click on Firefox button on the Top Left and click Options from the drop-down menu.
Click on Privacy tab.
Under History section, Click the drop down menu as shown below and select Use Custom Settings for History.
Now, select the check box that says Clear History when Firefox Exits. Click Ok.
If you want to customize the settings and delete only specific data, click on Settings right next to clear history on exit option.
Select the data you want to delete on Exit and click Ok.
Now, Firefox will delete all the selected data when you will exit Firefox automating a process many do manually.
Several other browsers have similar functionality so if you’re also a user of Microsoft Internet Explorer, be sure to check out guide for clearing History and Temporary files at exit for IE.