function show() {
	var ultag = this.childNodes.item(1);
	if ( ultag.style.display == 'block' ) {
	ultag.style.display = '';
	}
	else {
	ultag.style.display = 'block';
	}
}

function init() {
	var ullist = document.getElementById('menu').getElementsByTagName('ul');
		for ( var i = 0; i < ullist.length; i++ ) {
		ullist.item(i).parentNode.onclick = show;
	}
}

window.onload = init;