var ie4 = (document.all) ? true : false;
var ns4 = (document.layers) ? true : false;
var ns6 = (document.getElementById && !document.all) ? true : false;

function hidelayer(layer) {
  if (ie4) {document.all[layer].style.visibility = "hidden";}
  if (ns4) {document.layers[layer].visibility = "hide";}
  if (ns6) {document.getElementById([layer]).style.visibility = "hidden";}
}

function showlayer(layer) {
  if (ie4) {document.all[layer].style.visibility = "visible";}
  if (ns4) {document.layers[layer].visibility = "show";}
  if (ns6) {document.getElementById([layer]).style.visibility = "visible";}
}