Follow the steps its very easy to download 

youtube videos...

STEPS:

                             1) Go to youtube.com

                             2)Open the video which you want..

3)  Go to the address bar now you will see link like this http://www.youtube.com/watch?v=U8STgCviLe0  in this link replace Click between www. and youtube.com... and type ss and click enter

 

                                 4)Now you will get download link wait for 5 seconds... This is applicable for any video...