function Check() {
var Form = document.Contact;

  if (Form.Surname.value == '') {
  alert ('Please check your entry in the field "Surname"');
  Form.Surname.focus();
  return false;
  }

  if (Form.Street.value == '') {
  alert ('Please check your entry in the field "Street and No."');
  Form.Street.focus();
  return false;
  }

  if (Form.City.value == '') {
  alert ('Please check your entry in the field "zip/post code and city"');
  Form.City.focus();
  return false;
  }

  if (Form.Phone.value.length == '') var t_fehler = 1;;
  if (Form.eMail.value.length == '') var m_fehler = 1;

  if (t_fehler == 1 && m_fehler == 1) {
  alert ('To handle your message\n we need your telephone number\n or your eMail-adress');
  window.scrollTo(0,100);
  return false;
  }

  if ( t_fehler == 1 && (Form.eMail.value.indexOf('@') == -1 || Form.eMail.value.indexOf('.') == -1) ) {
  alert ('Please check your entry in the field "eMail"');
  Form.eMail.focus();
  return false;
  }

  if ( m_fehler == 1 && Form.Phone.value.length < 7)  {
  alert ('Please check your entry in the field "Phone"');
  Form.Phone.focus();
  return false;
  }

  if ( Form.Message.value == '')  {
  alert ('Please fill in your message');
  Form.Message.focus();
  return false;
  }
}