Scrollbar Annotation (path)

i.html

<div id="scrollbubble"></div>

<div style="height: 2000px">
    <p>Scroll<br />down<br />↓ ↓ ↓</p>
</div>

s.css

body {
     font: 12px/1.5 Helvetica, sans-serif;   
}

p {
    margin-right: 30px;
    text-transform: uppercase;
    text-align: right;
    font-size: 70px;
    font-weight: bold;
    line-height: 1;
    color: rgb(200, 200, 200);
}

#scrollbubble {
    display: none;
    position: fixed;
    top: 0;
    right: 20px;
    z-index: 500;
    padding: 3px 8px;
    background-color: #000;
    color: #FFF;
    border-radius: 3px;
}

#scrollbubble:after {
    content: " ";
    position: absolute;
    top: 50%;
    right: -8px;
    height: 0;
    width: 0;
    margin-top: -4px;
    border: 4px solid transparent;
    border-left-color: #000;
}

s.js

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 - $('#scrollbubble').height() / 2
       ;
 
    $('#scrollbubble')
        .css('top', distance)
        .text('Progress (' + Math.round(progress * 100) + '%)')
        .fadeIn(100)  
    ;

    // Fade out the annotation after 1 second of no scrolling.
    if (scrollTimer !== null) {
        clearTimeout(scrollTimer);
    }
    scrollTimer = setTimeout(function() {
        $('#scrollbubble').fadeOut();
    }, 1000);
});

// src = http://jsfiddle.net/michaelhue/7NAvm/7/light/