<html>
 <head>
  <script language="JavaScript">
   function redireccionar() {

    var url640x480 = "640.htm";
    var url800x600 = "800x600/Principal.htm";
    var url1024x768 = "Principal.htm";
    var nWdt = screen.width;
    var nHgh = screen.height;

    if ((nWdt == 640) && (nHgh == 480)) window.location.href= url640x480;
    else if ((nWdt == 800) && (nHgh == 600)) window.location.href= url800x600;
    else window.location.href= url1024x768;
   }
  </script>
 </head>
 <body onLoad="redireccionar()">
 </body>
</html>
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