function toggle(catName) {
	var obj = document.getElementById(catName);
	
	// if menu items are visibile, hide them
	if (obj.style.visibility == 'visible') {
		obj.style.visibility = 'hidden';
		obj.style.position = 'absolute';
	} 

	// if menu items are hidden, make them visible
	else {
		obj.style.visibility = 'visible';
		obj.style.position = 'relative';
		
		// close all other menus
		var menuIDs = new Array('For the Record', 'Selected Media', 'Books', 'MIT Links');
		for (var i=0; i<menuIDs.length; i++) {
			if (catName != menuIDs[i]) {
				obj = document.getElementById(menuIDs[i]);
				obj.style.visibility = 'hidden';
				obj.style.position = 'absolute';
			}
		}
	}
}