How to stop floating sidebar (Div Box) before footer using javascript?

I’m using this javascript and HTML to display a floating box in the top left corner of my webpage. But Its overlapping the #footer-wrap and moves down and down when scrolled. Could anyone help me to fix the code so that it stop exactly at #footer-wrap?

Javascript:

var ns = (navigator.appName.indexOf("Netscape") != -1);
var d = document;
function JSFX_FloatDiv(id, sx, sy)
{
    var el=d.getElementById?d.getElementById(id):d.all?d.all[id]:d.layers[id];
    var px = document.layers ? "" : "px";
    window[id + "_obj"] = el;
    if(d.layers)el.style=el;
    el.cx = el.sx = sx;el.cy = el.sy = sy;
    el.sP=function(x,y){this.style.left=x+px;this.style.top=y+px;};

    el.floatIt=function()
    {
        var pX, pY;
        pX = (this.sx >= 0) ? 0 : ns ? innerWidth :
        document.documentElement && document.documentElement.clientWidth ?
        document.documentElement.clientWidth : document.body.clientWidth;
        pY = ns ? pageYOffset : document.documentElement && document.documentElement.scrollTop ?
        document.documentElement.scrollTop : document.body.scrollTop;
        if(this.sy<0)
        pY += ns ? innerHeight : document.documentElement && document.documentElement.clientHeight ?
        document.documentElement.clientHeight : document.body.clientHeight;
        this.cx += (pX + this.sx - this.cx)/8;this.cy += (pY + this.sy - this.cy)/8;
        this.sP(this.cx, this.cy);
        setTimeout(this.id + "_obj.floatIt()", 40);
    }
    return el;
}
JSFX_FloatDiv("divTopRight", 10,30).floatIt();

Html:

<div id="divTopRight"     style="position:absolute">

<?php get_sidebar();?>

</div>

Also, how can I tweak it so that it overlaps header FULLY when page loads. Hope you’ll help me guys. Thx in advance.