subscribe form

<form name="mailing_list">
            <input type="text" name="email" id="emailform">
            <input type="button" id="go" value="Go!" onclick="subscribe();">
          </form>

          <script language="javascript">
          function subscribe() {
            var xmlhttp = new XMLHttpRequest();
            xmlhttp.open('POST', 'http://redlists.com/subscriptions/create', true);
            xmlhttp.send("<?xml version='1.0' encoding='UTF-8'?><subscription><list_id>16</list_id><email>" +
                document.mailing_list.email.value + "</email></subscription>");
            return true;
          }
          </script>