<script type="text/javascript">  
  function displayCurrentTime()  
  {  
    var date_obj = new Date();  
    var H = '' + date_obj.getHours();  
    H = H.length<2 ? '0' + H:H;  
    var M = '' + date_obj.getMinutes();  
    M = M.length<2 ? '0' + M:M;  
    var S = '' + date_obj.getSeconds();  
    S =S.length<2 ? '0' + S:S;  
    var clock = H + ':' + M + ':' + S;  
    document  
      .getElementById('time_element')  
        .innerHTML=clock;  
    //"перезапуск"  
    var t = setTimeout(displayCurrentTime,1000);  
  }  
  </script>  
  <div id="time_element"></div>  
  <script type="text/javascript">  
    displayCurrentTime();  
  </script>