function show()
{
  var Digital = new Date();
  var hours   = Digital.getHours();
  var minutes = Digital.getMinutes();
  var seconds = Digital.getSeconds();

  if (hours <= 9)
    hours = "0" + hours;
  if (minutes <= 9)
    minutes = "0" + minutes;
  if (seconds <= 9)
    seconds = "0" + seconds;
  
  document.getElementById("uhr").innerHTML = "Uhrzeit: " + hours + ":" + minutes + ":" + seconds;

  setTimeout("show()", 1000);
}

show();