Event.observe($F('mailformVornname'), 'click', function(e) {
  this.value='';  // this refers to the triggering element.
  return false; // stops the default behaviour (even in Safari!)
});
Event.observe('mailformNachname', 'click', function(e) {
  this.value='';  // this refers to the triggering element.
  return false; // stops the default behaviour (even in Safari!)
});
Event.observe('mailformTelefon', 'click', function(e) {
  this.value='';  // this refers to the triggering element.
  return false; // stops the default behaviour (even in Safari!)
});
Event.observe($F('mailform'), 'click', function(e) {
  $('mailformNachricht').clear();
  return false; // stops the default behaviour (even in Safari!)
});