<div id="progressbar" style="background-color:green; margin-top: 10px; width:0px; height:10px;"></div>
<script>
// set var to rep width of progress bar div
var dwidth=0;
// declare global variable for instance of Interval Timer so other funcs can access it.
IntervalId =0;
// grow progress bar each second
IntervalId = setInterval(function() { dwidth +=5; document.getElementById('progressbar').style.width = dwidth+'px';}, 1000);
// stop progress bar after 10 seconds
/* in real world an event handler would do this when iframe handling upload script loads response from upload */
setTimeout(function() { clearInterval ( IntervalId ); document.getElementById('progressbar').style.display='none' , 10000);
</script>