var openImg = 'pics/open.gif';
var closeImg = 'pics/closed.gif';

function preload(){
/*
if(document.images){
	Open = new Image(20,20);
	Closed = new Image(29,20);
	Open.src = "obrazky/open.gif";
	Closed.src = "obrazky/closed.gif"; 
	}

*/
}

function encodeN(cislo) {
if (cislo<10) return "0"+cislo;
else return "" + cislo;
}

// open/close a specific folder
function toggle(item){

   var elt = document.getElementById('menu'+encodeN(item));
   	var obr = document.getElementById("obr" + encodeN(item));
		if (elt.style.display == 'none'){			// if it's closed, open it
			elt.style.display = '';
			obr.src = openImg;
		}
		else {
			elt.style.display = 'none';				// if it's open, close it
			obr.src = closeImg;
		}
}