var current;

/**
 * Toggle the displayed menu
 */
function menu_unhide(whichLayer,old) {
	if (current == null) current = old;
	var oldmenu = document.getElementById('MID_'+current).style;
	oldmenu.display = 'none';

	if (document.getElementById) {
		// this is the way the standards work
		var newmenu = document.getElementById(whichLayer).value;
		var newmenu_div = document.getElementById('MID_'+newmenu).style;
		newmenu_div.display = 'block';
	}
	current = newmenu;
}