[trikadin]

<div id="1"></div>
<div id="2"></div>
<div id="3"></div>
<script>
t= document.getElementById(1);

timer= function(sec, num) {
 t.innerHTML= sec;
 if (sec == 0 && num == 3) {
  alert("Ба-бах!");
  return;
 } else if (sec==0) {
  t= document.getElementById(++num);
  sec= 11;
 }
 setTimeout(function() {timer(--sec, num)}, 1000);
};

timer(10, 1);
</script>