function news_signed(xmlhttp) {
  if (xmlhttp.readyState == 4) {
    if (xmlhttp.status == 200) {
      alert(xmlhttp.responseText);
      if (xmlhttp.responseText.indexOf('Email') == 0)
        document.getElementById('newsEmail').value = '';
    }
  }
}

function news_sign() {
  sign = document.getElementById('newsSignOut').checked ? 'out' : 'in';
  email = encodeURIComponent(document.getElementById('newsEmail').value);
  return !send_xmlhttprequest(news_signed, 'post', '/zasilani-novinek/', 'sign='+sign+'&email='+email+'&response=1');
}