var currentMenu = null;

function showMenu(elementId) {
	hideMenu();

	var menu = document.getElementById(elementId);
	menu.style.display="block";
	currentMenu = elementId;
}

function hideMenu() {
	if (currentMenu != null) {
		var menu = document.getElementById(currentMenu);
		menu.style.display="none";
		currentMenu = null;
	}
}