function shijian()
{

window.onload = tick;
}
function tick() {
var hours, minutes, seconds;
var intHours, intMinutes, intSeconds;
var today;
today = new Date();
intHours = today.getHours();
intMinutes = today.getMinutes();
intSeconds = today.getSeconds();

if (intMinutes < 10) {
minutes = "0"+intMinutes+":";
} else {
minutes = intMinutes+":";
}
if (intSeconds < 10) {
seconds = "0"+intSeconds+" ";
} else {
seconds = intSeconds+" ";
} 
timeString =intHours+":"+minutes+seconds;
Clock.innerHTML = timeString;
window.setTimeout("tick();", 100);
}