var nav=(navigator.appName=="Microsoft Internet Explorer")?"ie":"ns";
function mostrar(lay){
 if(nav=="ie"){
  eval("document.all."+lay+".style.visibility='visible'");
 }else{
  eval("document."+lay+".visibility='visible'");
 }
}

function ocultar(lay){
 if(nav=="ie"){
  eval("document.all."+lay+".style.visibility='hidden'");
 }else{
  eval("document."+lay+".visibility='hidden'");
 }
}