needs work.
First up, the good ol' if(this.hitTest(that)) isnt gonna cut it for the precise nature of a mario game (or any sidescroller for that matter). I advise looking into shape hitTest, bounds test, etc.
You get one point for humor because of the ridiculously stupid box that explains the controls. You have to explain the controls BEFORE people are able to jump and hit the box.
The hitTest on the castle flails were completely unacceptable, far too big (shape test was most definitely nessecary here) and hit mario even when he was well away from it.
NO MUSIC/SOUND IN THE PRELOADER!...its annoying.
And finally...in my personal opinion, dont use SMW sprites...theyre lame. If you have to use Mario sprites (or you COULD get someone to draw original characters, levels) use sprites from SMB3, the best Mario game ever (include Tanooki Suit or die).