function preload() {
    var menuimg01 = new Image();
    var menuimg02 = new Image();
    var menuimg03 = new Image();
    var menuimg04 = new Image();
    var menuimg05 = new Image();
    menuimg01.src = "/images/nav_ci_on.gif";
    menuimg02.src = "/images/nav_biz_on.gif";
    menuimg03.src = "/images/nav_es_on.gif";
    menuimg04.src = "/images/nav_svc_on.gif";
    menuimg05.src = "/images/nav_cu_on.gif";
}