By default, Firefox records everything from the list of websites you have visited, files you’ve downloaded to your active logins and cookies etc. Even though, this is a very useful feature, you may want to remove this history if you are using a public computer or you share your computer with someone else.
To clear the Firefox history:
1. Click on Menu button, select history option from that menu.
2. In the history sub-menu, select Clear Recent History option.
3. In Clear Recent History menu, select the time range to choose how much of your history Firefox will be removed.
4. Then click the arrow next to Details to choose exactly what data will be removed.
5. And When you are done, hit the clear now button. The window will automatically close and items you’ve selected will be removed.