if (document.images) {
   img1 = new Image(); img1.src = "images/eng_o.gif";
   img2 = new Image(); img2.src = "images/map_o.gif";
   img3 = new Image(); img3.src = "images/btn_01_o.gif";
   img4 = new Image(); img4.src = "images/btn_02_o.gif";
   img5 = new Image(); img5.src = "images/btn_03_o.gif";
   img6 = new Image(); img6.src = "images/mn_jigyo_o.gif";
   img7 = new Image(); img7.src = "images/mn_gaiyo_o.gif";
   img8 = new Image(); img8.src = "images/mn_kaisha_o.gif";
   img9 = new Image(); img9.src = "images/mn_page_o.gif";
   img10 = new Image(); img10.src = "images/mn_link_o.gif";
   img11 = new Image(); img11.src = "images/mn_bunseki_o.gif";
   img12 = new Image(); img12.src = "images/mn_seihin_o.gif";
   img13 = new Image(); img13.src = "images/mn_kankyo_o.gif";
   img14 = new Image(); img14.src = "images/mn_toukei_o.gif";
   img15 = new Image(); img15.src = "images/mn_kanko_o.gif";
   img16 = new Image(); img16.src = "images/mn_info_o.gif";
   img17 = new Image(); img17.src = "images/top_o.gif";
   img21 = new Image(); img21.src = "images/mn_user_o.gif";
}
function setImage(img, image) {
   if (img) {
      img.src = image;
   }
}