Buyrun:

<label id="minutes">00</label>:<label id="seconds">00</label>
<script type="text/javascript">
var minutesLabel = document.getElementById("minutes");
var secondsLabel = document.getElementById("seconds");
var totalSeconds = 0;
setInterval(setTime, 1000);

function setTime()
{
++totalSeconds;
secondsLabel.innerHTML = pad(totalSeconds%60);
minutesLabel.innerHTML = pad(parseInt(totalSeconds/60));
}

function pad(val)
{
var valString = val + "";
if(valString.length < 2)
{
return "0" + valString;
}
else
{
return valString;
}
}
</script>