if (window.attachEvent) {
	window.attachEvent("onload", showhide);
}

function showhide(layerID){
  if(document.getElementById){
	var targetElement = document.getElementById(layerID);
	var itemIsVisible = targetElement.style.visibility == 'visible';
		if (itemIsVisible){
			targetElement.style.visibility = 'hidden';
		} else {
			targetElement.style.visibility = 'visible';
		}
	}
}