Using unobtrusive javascript to provide "back to top" links without extra markup. (source: Web-Graphics)

<script type="text/javascript">
    function backToTop() {
        var x1 = x2 = x3 = 0;
        var y1 = y2 = y3 = 0;

        if (document.documentElement) {
            x1 = document.documentElement.scrollLeft || 0;
            y1 = document.documentElement.scrollTop || 0;
        }

        if (document.body) {
            x2 = document.body.scrollLeft || 0;
            y2 = document.body.scrollTop || 0;
        }

        x3 = window.scrollX || 0;
        y3 = window.scrollY || 0;

        var x = Math.max(x1, Math.max(x2, x3));
        var y = Math.max(y1, Math.max(y2, y3));

        window.scrollTo(Math.floor(x / 2), Math.floor(y / 2));

        if (x > 0 || y > 0) {
            window.setTimeout("backToTop()", 25);
        }
    }
</script>

<a href="#" onclick="backToTop(); return false">back to top</a>