var go_no = false;
function Ion(iid) {
        if (go_no) {
                patpat = eval("z" + iid + ".src");
                document [iid].src = patpat;
        }
}

function Ioff(iid) {
        if (go_no) {
                patpat = eval("y" + iid + ".src");
                document [iid].src = patpat;
        }
}
function IoffAll() {
    for (var i=1; i <= 3; i++) {
        Ioff('nav' + i);
    }
}