function startTime()
{
var today=new Date();
var h=today.getHours();
var m=today.getMinutes();
var s=today.getSeconds();
if (h>23)
{
h=h-24
}
if (h<10)
{
h="0"+h
}

// add a zero in front of numbers<10
m=checkTime(m);
s=checkTime(s);
document.getElementById('txt').innerHTML=h+":"+m+":"+s;
t=setTimeout('startTime()',500);
}

function checkTime(i)
{
if (i<10)
  {
  i="0" + i;
  }
return i;
}?