ie4 = ((navigator.appName == "Microsoft Internet Explorer") && (parseInt(navigator.appVersion) >= 4 )) 
ns4 = ((navigator.appName == "Netscape") && (parseInt(navigator.appVersion) >= 4 )) 

if (ns4) { 
layerRef="document.layers"; 
styleRef=""; 
} else { 
layerRef="document.all"; 
styleRef=".style"; 
} 

function afficher(calque) 
{ eval(layerRef + '["' + calque +'"]' + styleRef + '.visibility = "visible"'); } 

function masquer(calque) 
{ eval(layerRef + '["' + calque +'"]' + styleRef + '.visibility = "hidden"'); }