How to download Youtube Videos without any software from mobile or PC

 To Download Youtube Videos
Just remove 'm.' 
Or 'www.' From video url and add 'ss' infront of it and
enjoy downloading video in differnt qualites..
Example in Mobile : http:// m.youtube.com/watch?v=0LrT8N02vys 
Remove m. & Add ss http://ssyoutube.com/watch? v=0LrT8N02vys EG 
in PC : http://www.youtube.com/ watch?v=0LrT8N02vys 
Remove www. & Add ss http://ssyoutube.com/watch? v=0LrT8N02vys 
Choose 3gp 240p,flv 240p,flv 360p,mp4 360p,mp4 460p,mp4720p etc .. Thank you..