function checkForm(form, mand, email) {
  
  for (i=0;i<mand.length;i++) {
    elem = document.getElementById(mand[i]);
    if ( elem ) {
      elem.className += " formError";
    }
    
  }
  
  for (i=0;i<email.length;i++) {
    elem = document.getElementById(mand[i]);
    if ( elem ) {
      elem.className += " formError";
    }
  }
  alert("Bitte füllen Sie alle Pflichtfelder des Formulars aus.");
}