function do_check(f) {
  if (f.search_query.value == '') {
    f.search_query.focus();
    alert("Veuillez entrer au moins un mot à rechercher.");
    return false;
  }
  else
    return true;	
}

function check_search_block_form() {
  var f = document.forms['search_block_form'];
  return do_check(f);
}

function check_search_index_form() {
  var f = document.forms['search_index_form'];
  return do_check(f);
}