function toggle(obj) {
	var el = document.getElementById(obj);
	el.style.display = (el.style.display != 'none' ? 'none' : '' );
}

function layerOn(obj) {
	var el = document.getElementById(obj);
	el.style.display = '';
}
function layerOff(obj) {
	var el = document.getElementById(obj);
	el.style.display = 'none';
}

function highlight(obj) {
	var btnname = obj + '-btn';
	document.getElementById(obj).style.backgroundPosition = 'bottom'; 
	document.getElementById(btnname).style.backgroundPosition = 'bottom';
}

function highlightOff(obj) {
	var btnname = obj + '-btn';
	document.getElementById(obj).style.backgroundPosition = 'top';
	document.getElementById(btnname).style.backgroundPosition = 'top';
}