Try using
Code:
http://www.infiniteyoutube.com
to loop videos, it's very easy to do.
In the address bar, add the word "infinite" before the word "youtube". This is the easiest way to put Youtube videos on loop. When you are finished your address bar should be changed from:
Code:
http://www.youtube.com/watch?v=dMH0bHeiRNg
To
Code:
http://www.infiniteyoutube.com/watch?v=dMH0bHeiRNg
You can also go to infiniteyoutube.com and just paste in a link to the video or even search for videos.