</head>

[font=monospace]<script type="text/javascript">
  var scrollTimer = null;
$(window).scroll(function() {
  var viewportHeight = $(this).height(),
      scrollbarHeight = viewportHeight / $(document).height() * viewportHeight,
      progress = $(this).scrollTop() / ($(document).height() - viewportHeight),
      distance = progress * (viewportHeight - scrollbarHeight) + scrollbarHeight / 2 - $('#scroll').height() / 2;
    $('#scroll')
        .css('top', distance)
        .text(' (' + Math.round(progress * 100) + '%)')
        .fadeIn(600);
    if (scrollTimer !== null) {
        clearTimeout(scrollTimer);
    }
    scrollTimer = setTimeout(function() {
        $('#scroll').fadeOut(600);
    }, 1000);
});
//]]>
</script>[/font]

</head>

<div id='scroll'></div>