Download Youtube Video by Installing Script

friends in this post i will tell u how to download "youtube" vedios by installing script(only for firefox user) without going other website.This is the most easyest way to download youtube vedio.1. open firefox browser2. go to www.userscripts.org/scripts/source/8177.user.js& install the script3. open the youtube then select the vedio that u want to download.4. when u open the vedio below there