<div id="countdown">
<div id="minutes" style="float:left">00</div>
<div style="float:left">:</div>
<div id="seconds" style="float:left">00</div>
</div>
<div id="aftercount" style="display:none">Süre Doldu</div>

var sTime = new Date().getTime();
var countDown = 30;

function UpdateTime() {
var cTime = new Date().getTime();
var diff = cTime - sTime;
var seconds = countDown - Math.floor(diff / 1000);
if (seconds >= 0) {
var minutes = Math.floor(seconds / 60);
seconds -= minutes * 60;
$("#minutes").text(minutes < 10 ? "0" + minutes : minutes);
$("#seconds").text(seconds < 10 ? "0" + seconds : seconds);
} else {
$("#countdown").hide();
$("#aftercount").show();
clearInterval(counter);
}
}
UpdateTime();
var counter = setInterval(UpdateTime, 500);