// convert all characters to lowercase to simplify testing
    var agt=navigator.userAgent.toLowerCase();
    var is_major = parseInt(navigator.appVersion);
    var is_minor = parseFloat(navigator.appVersion);
    var is_nav  = ((agt.indexOf('mozilla')!=-1) && (agt.indexOf('spoofer')==-1)
                && (agt.indexOf('compatible') == -1) && (agt.indexOf('opera')==-1)
                && (agt.indexOf('webtv')==-1) && (agt.indexOf('hotjava')==-1));
    var is_navonly      = (is_nav && ((agt.indexOf(";nav") != -1) ||
                          (agt.indexOf("; nav") != -1)) );
    var is_gecko = (agt.indexOf('gecko') != -1);
    var is_ie     = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));
    var is_opera = (agt.indexOf("opera") != -1);
    var is_webtv = (agt.indexOf("webtv") != -1); 
    var is_TVNavigator = ((agt.indexOf("navio") != -1) || (agt.indexOf("navio_aoltv") != -1)); 
    var is_AOLTV = is_TVNavigator;
    var is_hotjava = (agt.indexOf("hotjava") != -1);

function ucitaj() {
for (var i = 1; i <= 5; i++) {
cat=('category'+i);
if (is_ie) document.all[cat].style.display = "none"; 
else if (is_nav)
document.getElementById([cat]).style.display = "none";
}
}

function brisi(a){
category_new=('category'+a);
ucitaj();
if (is_ie) document.all[category_new].style.display = "";
else if (is_nav) document.getElementById([category_new]).style.display = "";
}