Repostion Layer Problem

I am trying to repostion a frame when the page resizes. I know the code fires at the write time because i stuck an alert in there and i know that its the right object because i can change other properties of the layer, but not the postion.

Here is my code

Code:

---

function bannerResize()
{
        var divBanner = document.getElementById("banner");
       
        var dw = document.width ? document.width : document.documentElement.offsetWidth - 20;
       

        var i = ((dw - 800) / 2) + 700;

        divBanner.style.Left = i;
        ///alert("resize: " + i);
}

---

Any Ideas?

Thanks