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) {
  	page_01_over = newImage("images/menu/page_01-over.gif");
    page_02_over = newImage("images/menu/page_02-over.gif");
    page_03_over = newImage("images/menu/page_03-over.gif");
    page_07_over = newImage("images/menu/page_07-over.gif");
    page_08_over = newImage("images/menu/page_08-over.gif");
    page_09_over = newImage("images/menu/page_09-over.gif");
    page_10_over = newImage("images/menu/page_10-over.gif");
    page_11_over = newImage("images/menu/page_11-over.gif");
    page_12_over = newImage("images/menu/page_12-over.gif");
    page_13_over = newImage("images/menu/page_13-over.gif");
    preloadFlag = true;
  }
}