if (document.images) {
  image1on = new Image();
  image1on.src = "/.include/button/e/top_home_on.png";
  image2on = new Image();
  image2on.src = "/.include/button/e/top_ae2_on.png";
  image3on = new Image();
  image3on.src = "/.include/button/e/top_asca_on.png";
  image4on = new Image();
  image4on.src = "/.include/button/e/top_ginga_on.png";
  image5on = new Image();
  image5on.src = "/.include/button/e/top_sitemap_on.png";
  image6on = new Image();
  image6on.src = "/.include/button/e/top_english_on.png";

  image7on = new Image();
  image7on.src = "/ginga/.include/e/target_on.png";
  image8on = new Image();
  image8on.src = "/ginga/.include/e/report_on.png";
  image9on = new Image();
  image9on.src = "/ginga/.include/e/bibliography_on.png";

  image1off = new Image();
  image1off.src = "/.include/button/e/top_home_off.png";
  image2off = new Image();
  image2off.src = "/.include/button/e/top_ae2_off.png";
  image3off = new Image();
  image3off.src = "/.include/button/e/top_asca_off.png";
  image4off = new Image();
  image4off.src = "/.include/button/e/top_ginga_off.png";
  image5off = new Image();
  image5off.src = "/.include/button/e/top_sitemap_off.png";
  image6off = new Image();
  image6off.src = "/.include/button/e/top_english_off.png";

  image7off = new Image();
  image7off.src = "/ginga/.include/e/target_off.png";
  image8off = new Image();
  image8off.src = "/ginga/.include/e/report_off.png";
  image9off = new Image();
  image9off.src = "/ginga/.include/e/bibliography_off.png";
}

function turnOn(imageName) {
  if (document.images) {
    document[imageName].src = eval(imageName + "on.src");
  }
}

function turnOff(imageName) {
  if (document.images) {
    document[imageName].src = eval(imageName + "off.src");
  }
}