Videos automatically playing in Firefox? disable this permanently.....here's how

To change this setting, type about:config into Firefox’s address bar and press Enter. You will see a warning ..hit agree and then type “autoplay” into the search box. You’ll see a preference named “media.autoplay.enabled”, which will be set to True. Double-click that preference and it will change to False.
that will reset Firefox so it won't autoplay all those videos that are on websites and waste your bandwidth etc....