function arrow_toggle(obID)
{
  // toggle the article and the arrow :)
  Element.toggle('menu_drop' + obID +'');

  if(Element.visible('menu_drop' + obID +'')){
    document.getElementById('menu_'+obID+'').style.backgroundColor = '#4b5258';
  }
  else{
    document.getElementById('menu_'+obID+'').style.backgroundColor = '#4b5258';
  }
}