var timerRunning = false;
function stopclock (){
         if(timerRunning)clearTimeout(timerID);
         timerRunning = false;
}
function showtime () 
{
var now = new Date();
var hours = now.getHours();
var minutes = now.getMinutes();
var seconds = now.getSeconds();
var timeValue = "" + ((hours < 10) ? "0" : "") + hours;
timeValue += ((minutes < 10) ? ":0" : ":") + minutes;
timeValue += ((seconds < 10) ? ":0" : ":") + seconds;
document.clock.face.value = timeValue;
timerID = setTimeout("showtime()",1000);
timerRunning = true;
}
function startclock() 
{
stopclock();showtime();
}