codice:
<script language="JavaScript" type="text/JavaScript">
var timerID = null;
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;

        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();
}
</script>
ciao