function toggle (id){
  if (document.getElementById) {
    var mydiv = document.getElementById(id);
    mydiv.style.display = (mydiv.style.display=='block'?'none':'block');
  }
}

function hide (id){
  if (document.getElementById) {
    var mydiv = document.getElementById(id);
    mydiv.style.display = 'none';
  }
}

window.onload = function () {
// versteckt alle navipunkte
        hide('sub_gesundheit');
        hide('sub_hunde');
        hide('sub_katzen');
        hide('sub_kleinsaeuger');
        hide('sub_voegel');
        hide('sub_reptilien');
        hide('sub_fische');
        hide('sub_wildtiere');
        hide('sub_praxis');
}