function showLogin()
{
    new Effect.Move($('login'), { y:220, mode: 'relative', duration: .3 });
    $('username').activate();
}

function hideLogin()
{
    new Effect.Move($('login'), { y:-220, mode: 'relative', duration: .3 });
}

function enableCancel()
{
    $('cancel_login').observe('click', hideLogin);
}

document.observe('dom:loaded', function(){

    if($('sign_in'))
    {
        $('sign_in').observe('click', showLogin);
        $('cancel_login').observe('click', hideLogin);
    }

})