<div id="timer"></div>
<style>
#timer { color:#FF0000; }
</style>
<script>

(function (node, padd)
{
    var limit  = 360;
    var format = 'Hours:Minutes:Seconds';

    var timer = setInterval(function ()
    {
        if (limit-- > 0)
        {
            var date = new Date(limit * 1000);

            node.innerHTML = format.replace(/\w+/g, function (m)
            {
                var s = date['getUTC' + m]().toString(10);

                return padd[s.length] + s;
            });
        }
        else
        {
            clearInterval(timer);
        }
    }, 1000);
}(document.getElementById('timer'), ['00', '0', '', '', '']));

</script>