//画像のプリロード

tsuru_HeaderImageNormal = new Array();
tsuru_HeaderImageOver   = new Array();
tsuru_HeaderImageName   = new Array("bt_hd_top","bt_hd_around","bt_hd_map","bt_hd_industry","bt_hd_event","bt_hd_history");


for(tsuru_count=0;tsuru_count<tsuru_HeaderImageName.length;tsuru_count++) {
//通常時 画像
  tsuru_HeaderImageNormal[tsuru_count]     = new Image();
  tsuru_HeaderImageNormal[tsuru_count].src = "./images/"+ tsuru_HeaderImageName[tsuru_count] + "_normal.gif";
//マウスオーバー時 画像
  tsuru_HeaderImageOver[tsuru_count]       = new Image();
  tsuru_HeaderImageOver[tsuru_count].src   = "./images/"+ tsuru_HeaderImageName[tsuru_count] + "_over.gif";
}

function tsuru_HeaderImageChange(ImageNo, ImageEvent) {
  if(ImageEvent=="over") {
    document.images[tsuru_HeaderImageName[ImageNo]].src = tsuru_HeaderImageOver[ImageNo].src;
  } else if(ImageEvent=="out") {
    document.images[tsuru_HeaderImageName[ImageNo]].src = tsuru_HeaderImageNormal[ImageNo].src;
  }
}