Yes I do, chrome is the browser I use. I found out that it lags a lot on both firefox and safari. I don't get it. Why is it only working "kind of" properly in chrome?! I hate html5/java script!
EDIT: I solved the boss-thing by making an own boss class with it's own collision function and draw function and it worked! Now it's only the different browser thing left until I feel satisfied with java script.