var tick;
  function stop() {
  clearTimeout(tick);
  }
  function clock() {
  var ut=new Date();
  var h,m,s;
  var time="        ";
  h=ut.getHours();
  m=ut.getMinutes();
  s=ut.getSeconds();
  if(s<=9) s="0"+s;
  if(m<=9) m="0"+m;
  if(h<=9) h="0"+h;
  time+=h+":"+m+" ";
  document.getElementById('clock').innerHTML=time;
  tick=setTimeout("clock()",1000); 
  }