var layerRef = "document[";
var layerRef2 = "]";
var showRef = "show";
var hideRef = "hide";
if(document.layers) {
	var layerRef = "document["; var layerRef2 = "]"; 
	var showRef = "show"; 
	var hideRef = "hide";
}
else if(document.all) {
	var layerRef = "document.all[";
	var layerRef2 = "].style";
	var showRef = "visible";
	var hideRef = "hidden";
}
else {
	var layerRef = "document.getElementById("; var layerRef2 = ").style";
	var showRef = "visible"; var hideRef = "hidden";
}

function hideLayer(layerName) {
	eval( layerRef + '"' + layerName + '"' + layerRef2 + '.visibility = ' + '"' + hideRef + '"' )
}

function showLayer(layerName) {
	eval( layerRef + '"' + layerName + '"' + layerRef2 + '.visibility = ' + '"' + showRef + '"' )
}
	
function swMarker(what) {
	document.images["marker"].src = eval(what + ".src")
}

function toggleLayer(whichLayer) {
	if(eval( layerRef + '"' + whichLayer + '"' + layerRef2 + '.visibility == ' + '"' + showRef + '"' )) {	
		hideLayer(whichLayer);
	}
	else {
		showLayer(whichLayer);
	}
}