var activeLayer;
var timer;
var timeout=50;
function showLayer(id){
	stopTimer();
	if(activeLayer!=document.getElementById(id)){
		hideLayer();
		activeLayer=document.getElementById(id);
		activeLayer.style.visibility = "visible";
	}
}
function hideLayer(){
	if(activeLayer){
		activeLayer.style.visibility = "hidden";
		activeLayer=null;
	}
}
function startTimer(){
	timer=setTimeout("hideLayer()", timeout);
}
function stopTimer(){
	clearTimeout(timer);
}