function showHideMenu(itemID, stateMarker, selectedItem) {
    var el = document.getElementById(itemID);
    if (el.style.display != 'block') {
        el.style.display = 'block';
        document.getElementById(stateMarker).innerHTML = "-";
    }
    else {
        el.style.display = 'none';
        selectedItem.style.backgroundPosition = 'top';
        document.getElementById(stateMarker).innerHTML = "+";
    }
}