Step 1> open mozilla firefox..search google for FIREFOX ADDONS..select the url – addons.firefox.com(or u cn directly paste this url in ur address bar)
2>on the opened webpage search for FIREFOX ADDONS…a list of addons with details will appear..choose one of ur choice.
3>click on ADDTO FIREFOX…a dialogue box will appear..click on INSTALL NOW..it will b installed within seconds.
4>u will be asked to restart Firefox; do so.
5> open any youtube video with firefox… u will get a DOWNLOAD VIDEO button!!
NOTE:this method only works for firefox(may also work for IE)
enjoy downloading.
Tech. Is fun!!(: