function get_innerheight()
{
 if (document.body.scrollHeight > 0) // all - maybe
  scnHeight = document.body.scrollHeight;

  else if (self.innerHeight) // all except Explorer
  scnHeight = self.innerHeight;
 
  else if (document.documentElement && document.documentElement.clientHeight) // Explorer 6 Strict
  scnHeight = document.documentElement.clientHeight;
 
  return scnHeight;
}

// A div-et megjelenítő, elrejtő kód:
function switch_overlay_all()
{
  OA = document.getElementById('overlay_all');
  OA.style.height = get_innerheight()+'px';
  select = document.getElementById('konyv2');
  OA_felso = document.getElementById('overlay_all_felso');


//select menü eltüntetése
     if(select.style.visibility == 'visible')
       select.style.visibility = 'hidden';
     else
       select.style.visibility = 'visible';

//felső, form réteg vizsgálata     
     if(OA_felso.style.visibility == 'hidden')
       OA_felso.style.visibility = 'visible';
     else
       OA_felso.style.visibility = 'hidden';

//alsó, átlátszó réteg vizsgálata
     if(OA.style.visibility == 'hidden')
       OA.style.visibility = 'visible';
     else
       OA.style.visibility = 'hidden';
}

function switch_overlay_all_felir()
{
  OA = document.getElementById('overlay_all');
  OA.style.height = get_innerheight()+'px';
  select = document.getElementById('konyv2');
  OA_felso_felir = document.getElementById('overlay_all_felso_felir');

//select menü eltüntetése
     if(select.style.visibility == 'visible')
       select.style.visibility = 'hidden';
     else
       select.style.visibility = 'visible';

//felső, form réteg vizsgálata     
     if(OA_felso_felir.style.visibility == 'hidden')
       OA_felso_felir.style.visibility = 'visible';
     else
       OA_felso_felir.style.visibility = 'hidden';

//alsó, átlátszó réteg vizsgálata
     if(OA.style.visibility == 'hidden')
       OA.style.visibility = 'visible';
     else
       OA.style.visibility = 'hidden';
}