function openWindow(link) // inspired by porneL - http://pornel.net/pups/
{
  try
  {
    var new_window = window.open(link, '_blank');
    if(new_window) return false;
  }
  catch(e){}
  return true;
}

function checkRequiredFields(form_id)
{
  ok = true;
  fields = document.getElementsByTagName('input');
  for(var i in fields) if(fields[i].className=='text required')
  {
    if(fields[i].parentNode.parentNode.parentNode.id==form_id && !fields[i].value) ok = false;
  }
  fields = document.getElementsByTagName('textarea');
  for(var i in fields) if(fields[i].className=='required')
  {
    if(fields[i].parentNode.parentNode.parentNode.id==form_id && !fields[i].value) ok = false;
  }
  if(ok)
  {
    document.getElementById('submit_'+form_id).disabled = 'disabled';
    return true;
  }
  alert('Musisz wypełnić wszystkie wymagane pola (oznaczone gwiazdką).');
  return false;
}