var active_layer="";

function my_zmiana(symbol,alayer){

  if(alayer == active_layer){
    document.all[active_layer].style.display = 'none';
    active_layer='';
  } else {
    if(active_layer!=""){
      document.all[active_layer].style.display = 'none';
    }
    active_layer=alayer;
    document.all[active_layer].style.display = '';
  }

//    document.all[obr].src = 'site_img/cl.gif';
//    document.all[obr].src = 'site_img/cl.gif';
}