Deerua about Coding -> getBoxObjectFor для FireFox 3.6 и выше

    if(typeof document.getBoxObjectFor == "undefined") {
        document.getBoxObjectFor = function(elem) {
            var obj = new Object;
            var rect = elem.getBoundingClientRect();
            obj.y = rect.top;
            obj.x = rect.left;
            obj.width =Math.abs(rect.right-rect.left);
            obj.height = Math.abs(rect.bottom-rect.top);
            return obj;
        }
    }