function start() { 
  show_clock();
  initTip();
}
function toggleDisplay(element){
for ( var i=0; i<element.length; i++ ) {
	var el=document.getElementById(element[i]);
	if (el.style.display=="block"){
		el.style.display="none";
		}
	else {
			el.style.display="block";
		}
	}
}
function changeClass(id, className) {
	var el=document.getElementById(id);
	el.className=className;
}