function validate() {
    var email = document.getElementById('email').value;
    var isEmail = /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/i;
    if (isEmail.test(email)) {
      return true;
    }
    alert('Please enter a valid email.');
    return false;
  }