Javascript Countdown Timer

<div style="float: right;">
   Time Remaining 
   <b id="min">0</b> minute(s) 
   <b id="sec">0</b> second(s)
</div>
<script>
dm=0;dd=5;
function remaining(){
   if(dd>=0){
      if(dm<0){
         alert('time is out');
      }else{
         document.getElementById('min').innerHTML=dm;
         document.getElementById('sec').innerHTML=dd;
         if(dd<=0){
            dd=60;
            dm--;
         }
         dd--;
         setTimeout('remaining()',1000);
      }
   }
}
remaining(); </script>