The script doesn't seem to work with the latest Magento. Here's what I use:

var loginForm = document.getElementById('loginForm');
var username = document.getElementById('username');
var login = document.getElementById('login');
var dummy = document.getElementById('dummy');

if (document.getElementById('page-login') && loginForm && username && dummy && login) {
    loginForm.autocomplete = 'on';
    username.autocomplete = 'username';
    dummy.remove();
    login.autocomplete = 'current-password';
}