var minuly = 'uvod' ;
var isNS4 = (navigator.appName == "Netscape" && parseInt(navigator.appVersion) == 4);
var isNS5 = (navigator.appName == "Netscape" && parseInt(navigator.appVersion) >= 5);
var insall = (isNS4) ? "layers." : (isNS5) ? "getElementById(\"" : "all.";
var insstyle = (isNS4) ? "" : (isNS5) ? "\").style" : ".style"; 

function zobraz(ident) { 
if(parseInt(navigator.appVersion) >= 4) { 
el = eval("document." + insall + [ident] + insstyle );
el.visibility = "visible";

if(minuly != ident) {
el = eval("document." + insall + [minuly] + insstyle );
el.visibility = "hidden";
minuly = ident }

} }