// verbergen/tonen van individuele onderdelen van het tree menu
function showHide(id, elem, src) {
	obj = document.getElementById(id).style;
	
	std = "images/bullet.gif";
	alt = "images/bullet_down.gif";
	folder = "images/folder.gif";
	page = "images/page.gif";
	
	if(src.tagName == "IMG") {
		obj.display = obj.display == "none" ? "" : "none";	
		elem.src = elem.src != folder && elem.src != page && elem.src.indexOf(std) != -1 ? elem.src.replace(std, alt) : elem.src.replace(alt, std);
	}
	else {
		obj.display = "";
		elem.src = elem.src.replace(std, alt);
	}
	
	collapsed = false;
}