var ns4 = false;
var ie4 = false;
var en6 = false;

if (document.all) {
  ie4 = true;
}
else if (document.layers) {
  ns4 = true;
}
else if (document.getElementById) {
  en6 = true;
}

function muestraCapa (idcapa)
{
  if (ie4) {
    var oObject = document.all.item(idcapa);
    if (oObject != null) {
      if (oObject.style.visibility != null) {
        oObject.style.visibility = "visible";
      }
    }
  }
  if (ns4) {
    capavis = document.layers[idcapa].visibility = "show";
  }
  if (en6) {
    capavis = document.getElementById(idcapa).style.visibility = "visible"; 
  }
}

function ocultaCapa (idcapa)
{
  if (ie4) {
    var oObject = document.all.item(idcapa);
    if (oObject != null) {
      if (oObject.style.visibility != null) {
        oObject.style.visibility = "hidden";
      }
    }
  }
  if (ns4) {
    capavis = document.layers[idcapa].visibility = "hide";
  }
  if (en6) {
    capavis = document.getElementById(idcapa).style.visibility = "hidden";
  }
}