var menuItems = new Array("about", "programs", "calendars", "members");

function showDropDown(item) {
    hideDropDown();
    document.getElementById(item).style.visibility = "visible";
}

function hideDropDown() {
    for (var i=0; i<menuItems.length; i++) {
        document.getElementById(menuItems[i]).style.visibility = "hidden";
    }
}