var browserType;

if (document.layers) {browserType = "nn4"}
if (document.all) {browserType = "ie"}
if (window.navigator.userAgent.toLowerCase().match("gecko")) {
   browserType= "gecko"
}

function hide() {
  if (browserType == "gecko" )
     document.poppedLayer = 
         eval('document.getElementById("enmedio")');
  else if (browserType == "ie")
     document.poppedLayer = 
        eval('document.getElementById("enmedio")');
  else
     document.poppedLayer =   
        eval('document.layers["enmedio"]');
  document.poppedLayer.style.visibility = "hidden";
}

function show( vimagen ) {
  if (browserType == "gecko" )
     document.poppedLayer = 
         eval('document.getElementById("enmedio")');
  else if (browserType == "ie")
     document.poppedLayer = 
        eval('document.getElementById("enmedio")');
  else
     document.poppedLayer = 
         eval('document.layers["enmedio"]');
  document.getElementById('laimagen').src = "/cms/wp-content/uploads/2009/11/cargando.gif";
  document.poppedLayer.style.visibility = "visible";
  var t=setTimeout("",3000);
  document.getElementById('laimagen').src = vimagen;
}