function cas () {
	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
	window.document.getElementById("cas").innerHTML = timeValue;	
}

cas();
window.setInterval("cas()", 1000);