function setCookie(c_name, c_value ) {

	document.cookie = c_name + "=" + escape( c_value ) + "; path=/";
}

function getCookie(c_name) {
	if (document.cookie.length>0)
	  {
	  c_start=document.cookie.indexOf(c_name + "=");
	  if (c_start!=-1)
		{ 
		c_start=c_start + c_name.length+1; 
		c_end=document.cookie.indexOf(";",c_start);
		if (c_end==-1) c_end=document.cookie.length;
		return unescape(document.cookie.substring(c_start,c_end));
		} 
	  }
	return "";
}

function toggleLeftNav(ilayer){ 
	if (ilayer == 1) {
		document.getElementById('leftnav1').style.visibility='visible';
		document.getElementById('leftnav2').style.visibility='hidden';
		setCookie("lukenav", "1977");
		return null;
	} else {
		document.getElementById('leftnav1').style.visibility='hidden';
		document.getElementById('leftnav2').style.visibility='visible';
		setCookie("lukenav", "roper");
		return null;
	}
}

//if the cookie is set to roper then show the second nav, otherwise just ignore
function f_checknavchoice() {
	if(getCookie("lukenav") == "roper") {
		document.getElementById('leftnav1').style.visibility='hidden'
		document.getElementById('leftnav2').style.visibility='visible'
	} else {
		document.getElementById('leftnav1').style.visibility='visible'
		document.getElementById('leftnav2').style.visibility='hidden'
	}
}
	

//now add event listeners for onload
if (window.addEventListener) {
	window.addEventListener ("load",f_checknavchoice,false); //W3c like FF
} else if (window.attachEvent) {
	window.attachEvent ("onload",f_checknavchoice); // Microsoft
} else {
	window.onload = f_checknavchoice; //others
}