function byId(id) {
    return document.getElementById ? document.getElementById(id) : false;
}

function allById(ids) {
    var elements = new Array(ids.length);
    for (var i = 0; i < ids.length; ++i) {
        elements[i] = byId(ids[i]);
        if (!elements[i]) return false;
    }
    return elements;
}