var ns4,ie4,en6;
  ns4=(document.layers)? true:false
  ie4=(document.all)? true:false
  en6=(document.getElementById)? true:false
function muestra_capa(idcapa){
  if ( document.forms[0].capa.value ){
  	oculta_capa( document.forms[0].capa.value );
  }
  if (ns4) capavis=document.layers[idcapa].visibility='show';
  if (ie4) capavis=eval('document.all.' + idcapa + '.style.visibility="visible"');
  if (en6) capavis=eval('document.getElementById(idcapa).style.visibility="visible"');
  document.forms[0].capa.value= idcapa;
}
function oculta_capa(idcapa){
  if (ns4) capavis=document.layers[idcapa].visibility='hide';
  if (ie4) capavis=eval('document.all.' + idcapa + '.style.visibility="hidden"');
  if (en6) capavis=eval('document.getElementById(idcapa).style.visibility="hidden"');
}