function newImage(arg) {
  if (document.images) {
    rslt = new Image();
    rslt.src = arg;
    return rslt;
  }
}
function changeImages() {
  if (document.images && (preloadFlag == true)) {
    for (var i=0; i<changeImages.arguments.length; i+=2) {
      document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
    }
  }
}
var preloadFlag = false;
function preloadImages() {
  if (document.images) {
    t_01  = newImage("images/btn-01-en-p.jpg");
    t_02  = newImage("images/btn-02-en-p.jpg");
    t_03  = newImage("images/btn-03-en-p.jpg");
    t_04  = newImage("images/btn-04-en-p.jpg");
    t_05  = newImage("images/btn-05-en-p.jpg");
    t_06  = newImage("images/btn-06-en-p.jpg");
    t_07  = newImage("images/btn-07-en-p.jpg");

    b_01  = newImage("images/btn-mapa-01-en-p.jpg");
    b_02  = newImage("images/btn-mapa-02-en-p.jpg");
    b_03  = newImage("images/btn-mapa-03-en-p.jpg");
    b_04  = newImage("images/btn-mapa-04-en-p.jpg");
    b_05  = newImage("images/btn-mapa-05-en-p.jpg");
    b_06  = newImage("images/btn-mapa-06-en-p.jpg");
    b_07  = newImage("images/btn-mapa-07-en-p.jpg");

    r_01  = newImage("images/btn-big-01-en-p.jpg");
    r_02  = newImage("images/btn-big-02-en-p.jpg");
    r_03  = newImage("images/btn-big-03-en-p.jpg");

    preloadFlag = true;
  }
}