function showSubmenu(arg) {
    if (!document.getElementById("MenuItem" + arg)) return false;

    var tempImg = document.getElementById("MenuItem" + arg);
    var tempSrc = tempImg.getAttribute("src").replace(".gif", "_on.gif");
    tempImg.setAttribute("src", tempSrc);

    if (arg <= 5) {
        if (!document.getElementById("gnb_submenu" + arg)) return false;
        document.getElementById("gnb_submenu" + arg).style.display = "block";
    }

    return false;
}

function hideSubmenu(arg) {
    if (!document.getElementById("MenuItem" + arg)) return false;

    var tempImg = document.getElementById("MenuItem" + arg);
    var tempSrc = tempImg.getAttribute("src").replace("_on.gif", ".gif");
    tempImg.setAttribute("src", tempSrc);

    if (arg <= 5) {
        if (!document.getElementById("gnb_submenu" + arg)) return false;
        document.getElementById("gnb_submenu" + arg).style.display = "none";
    }

    return false;
}