Shake object with tag form w/o jquery

Shake_form.js

addLoadEvent = function (func) {
    if (typeof jQuery != "undefined") jQuery(document).ready(func);
    else if (typeof wpOnload != 'function') {
        wpOnload = func;
    } else {
        var oldonload = wpOnload;
        wpOnload = function () {
            oldonload();
            func();
        }
    }
};

function s(id, pos) {
    g(id).left = pos + 'px';
}

function g(id) {
    return document.getElementById(id).style;
}

function shake(id, a, d) {
    c = a.shift();
    s(id, c);
    if (a.length > 0) {
        setTimeout(function () {
            shake(id, a, d);
        }, d);
    } else {
        try {
            g(id).position = 'static';
            wp_attempt_focus();
        } catch (e) {}
    }
}
addLoadEvent(function () {
    var p = new Array(15, 30, 15, 0, -15, -30, -15, 0);
    p = p.concat(p.concat(p));
    var i = document.forms[0].id;
    g(i).position = 'relative';
    shake(i, p, 20);
});