var interval, num;

function timer() {
	num = 1;
	autoTabs();
	interval = setInterval("autoTabs();", 15000 );
}

function autoTabs() {
	changeLayer(num,false);
	num++;
	if(num>4){num=1};

}


function changeLayer(tabNum,cleared) {
	
	for(i=1;i<5;i++) {
		document.getElementById("cycle"+i).style.display = "none";
		
	}
	document.getElementById("cycle"+tabNum).style.display = "block";
	
	
}