Contador
by Pasky Org
HTML
Contador: <span id="contador"> </span>
JavaScript
var t = Math.floor(new Date()/1000 + 3600);
var timeleft = 300;
var downloadTimer = setInterval(function(){
document.getElementById("contador").textContent = --timeleft;
if(timeleft <= 0)
clearInterval(downloadTimer);
},1000);