function zobraz_znacku(menu)
{
    var o1 = document.getElementById("h_"+menu+"_top");
    var o2 = document.getElementById("h_"+menu+"_bottom");
    o1.style.display='block';
    o1.style.visibility='visible';
    
    o2.style.display='block';
    o2.style.visibility='visible';
};
            
function schovej_znacku(menu)
{
    var o1 = document.getElementById("h_"+menu+"_top");
    var o2 = document.getElementById("h_"+menu+"_bottom");
    o1.style.display='none';
    o1.style.visibility='hidden';
    
    o2.style.display='none';
    o2.style.visibility='hidden';
};