Setting a div position in $(document).ready()?

Setting a div position in $(document).ready()?

I have a 'window' that is moveable on this test page:

 http://www.hindbrain.net/ex11.php

I'm trying to use cookies to store the window positions in the mouseup function. That part is working fine. The problem is that I can't figure out how to locate the window to the x,y variables after returning from checkCookie(). I've tried a few things and they are commented out if you look at the javascript. I thought that this would work, but it doesn't:

$(".window1")[0].offsetLeft = x;
$(".window1")[0].offsetTop = y;

Can someone explain the correct way to do this? Also, why is the '[0]' required? I found that I need this from firebug, but don't know why.

thanks,
Bob