Why wont IE display this correct

http://jsfiddle.net/DalexL/NG6ty/

The link above shows what I'm working with. I currently have a hot air ba开发者_运维知识库lloon that needs to fly around the page. It works fine in Google Chrome but doesn't even move or anything inside of IE.

What am I doing wrong here?

In this line:

width: "+="+(newTop),

you should remove the comma

width: "+="+(newTop)

IE usually is more tolerant to sloppy code, but in this case was working fine for other browsers, even though the extra comma was syntactically incorrect. Removing it worked fine for IE7. I guess IE9 "forgives" this kind of syntax error