How well does this work?

I have just started to create an isometric game using javascript and html5, later I will add php and MySQL so I can make it to a proper game, now it’s just a test project. But I would like to know if there is any problems with it now, the fps you get, and how accurate the mouse is.

EDIT: ops forgot the link ^^"
http://creaturecontroller.com/battle/arena.php