function changeNav (tab){
	if (tab==tabbSelect) return;
	
	var divName;
	tabbSelect = tab;
	var dvar = "nav_"+tab;

	var divTags =  document.getElementsByTagName("div")  ;
	for (var i = 0; i < divTags.length ; i++)	{
		divName = divTags[i].id;
		
	if (divName.substring(0, 3)=="nav") {
			poppedLayer=document.getElementById(divName);
			poppedLayer.style.visibility = "hidden";
			}

	} 
	
	poppedLayer=document.getElementById(dvar);
	poppedLayer.style.visibility = "visible";
}


function scrollTab (dir){
	var divName;
	tabbSelect = tab;
	var dvar = "tabb_"+tab;

	var divTags =  document.getElementsByTagName("div")  ;
	for (var i = 0; i < divTags.length ; i++)	{
		divName = divTags[i].id;
		
		if (divName.substring(0, 9)=="tabb") {
			poppedLayer=document.getElementById(divName);
			poppedLayer.style.visibility = "hidden";
			}

	} 
	
	poppedLayer=document.getElementById(dvar);
	poppedLayer.style.visibility = "visible";
}