function desaparecer(capa)
{

var obj = document.getElementById("botonNoVisible"+capa);
obj.style.display = "none";
var obj = document.getElementById("botonVisible"+capa);
obj.style.display = "block";
}
function aparecer(capa)
{
var obj = document.getElementById("botonNoVisible"+capa);
obj.style.display = "block";
var obj = document.getElementById("botonVisible"+capa);
obj.style.display = "none";
}

/* enlaces externos */
function externalLinks() {
alert('asfasdf');
 if (!document.getElementsByTagName) return;
 var anchors = document.getElementsByTagName("a");
 for (var i=0; i<anchors.length; i++) {
   var anchor = anchors[i];
   if (anchor.getAttribute("href") &&
       anchor.getAttribute("rel") == "external")
     anchor.target = "_blank";
 }
}