// Browser detection

      // Internet Explorer

      var ie  = document.all != null;  //ie4 and above

      var ie5 = document.getElementById && document.all;

      var ie6 = document.getElementById && document.all&&(navigator.appVersion.indexOf("MSIE 6.")>=0);

      // Netscape

      var ns4 = document.layers != null;

      var ns6 = document.getElementById && !document.all;

      var ns  = ns4 || ns6;

      // Firefox

      var ff  = !document.layers && !document.all;

      // Opera

      var op  = navigator.userAgent.indexOf("opera")>0;

      var op7 = op && operaVersion() <= 7;

      var op8 = op && operaVersion()>= 8;

      // Detects the Opera version

      function operaVersion() {

          agent = navigator.userAgent;

          idx = agent.indexOf("opera");

          if (idx>-1) {

              return parseInt(agent.subString(idx+6,idx+7));

          }

      }

if (ie6) {
alert("Tienes Internet Explorer 6. Para visualizar esta p\u00e1gina correctamente, actualiza a la \u00faltima versi\u00f3n o cambiate a Mozilla Firefox.");
}