low quality on my video

Hi

i am a totally newbie to video creation so i am probably going to post some basic questions that however i can't figure out myself.

I make simple videos with imovie. The problem is that the quality when i upload it to youtube and to my site is very low.

check it outhttp://www.youtube.com/watch?v=2uSYPyRRtU0

Can someone suggest me why?

Thanks

PaoloG<span style="white-space: pre;"> </span>