function prepRollover(img, overDefault)
{
    img.overSrc = img.src.split('.gif').join('-over.gif');
    if (overDefault)
    {
        img.onload = null;
        img.src = img.overSrc;
        return;
    }
    img.outSrc = img.src;
    new Image().src = img.overSrc;
    img.onmouseover = function(){this.src=this.overSrc;}
    img.onmouseout = function(){this.src=this.outSrc;}
    img.onload = null;
}