//global variables
var layerRef="null",layerStyleRef="null",styleSwitch="null";

if (navigator.appName == "Netscape") {
    layerStyleRef="layer.";
    layerRef="document.layers";
    styleSwitch="";
}
else {
    layerStyleRef="layer.style.";
    layerRef="document.all";
    styleSwitch=".style";
}

function showLayer(layerName) {
       eval(layerRef+'["'+layerName+'"]'+styleSwitch+'.visibility="visible"');
}

function hideLayer(layerName) {
       eval(layerRef+'["'+layerName+'"]'+styleSwitch+'.visibility="hidden"');
}