function validateForm(check_form) {
  
  if (typeof check_form.elements['data[poster]'] == "object") {
      var poster = check_form.elements['data[poster]'].value;
      var elment_name = 'data[poster]';
  } else if (typeof check_form.elements['data[from_name]'] == "object") {
      var poster = check_form.elements['data[from_name]'].value;
      var elment_name = 'data[from_name]';   
  }
   
  if (poster.length < 3) {
      alert("Bitte einen gültigen Namen eingeben ( größer 2 Zeichen) !");
      set_focus(check_form,elment_name);
      return false;
  }

  var message = check_form.elements['data[message]'].value;
  if (message.length < 10) {
      alert("Bitte eine gültige Mitteilung eingeben ( mehr als 10 Zeichen )!");
      set_focus(check_form,'data[message]');
      return false;
  }

  // validate email adress
  if (check_form.elements['data[email]'].value > '') {
      if (!isValidEmail(check_form.elements['data[email]'].value)) {
          alert("Bitte eine gültige Email Adresse eingeben !");
          set_focus(check_form,'data[email]');
          return false;
      }
  }    

  return true;
}


function isValidEmail(emailAddress) {
   var reg = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
   return reg.test(emailAddress);
}

function set_focus(check_form,element_name) {

   var obj = check_form.elements[element_name];
   obj.style.backgroundColor = '#FFE4E1';
   obj.style.border = '1px solid #000';
   obj.focus();
   obj.select();
}