Checkout this video:
1.Open the Firefox browser and go to the Tools drop-down menu. If you don’t see the Tools menu, press Alt+T on your keyboard.
2.Select Options from the Tools drop-down menu.
3.When the Options window opens, select the Content tab at the top of the window.
In the address bar, type about:config and press EnterReturn. The about:config “This might void your warranty!” warning page may appear. Click I accept the risk! to continue to the about:config page.
Select the Content tab
To access the content settings in Firefox, open the menu by clicking on the three stacked lines in the upper right-hand corner of the browser followed by “Options.” You can also enter “about:preferences” in the search bar. Once you’re in the options menu, select “Content” from the list on the left.
1. Open Firefox and enter “about:config” in the address bar.
2. Click the button promising to be careful.
5. Close the about:config tab/window and refresh your browser window to make the changes take effect.
Open the Firefox browser.
In the address bar at the top, type about: config and press Enter.
A warning page may appear. Click I accept the risk!.
Close the about: config page.