/* 画像の先行読み込み */
if(document.images) {
 var imgs = new Array();
 imgs[0] = new Image();  imgs[0].src = "http://1000marketing.com/img/left_01.jpg"; //画像パスを入力
 imgs[1] = new Image();  imgs[1].src = "http://1000marketing.com/img/left_01_m.jpg";
 imgs[2] = new Image();  imgs[2].src = "http://1000marketing.com/img/left_02.jpg";
 imgs[3] = new Image();  imgs[3].src = "http://1000marketing.com/img/left_02_m.jpg";
 imgs[4] = new Image();  imgs[4].src = "http://1000marketing.com/img/left_03.jpg";
 imgs[5] = new Image();  imgs[5].src = "http://1000marketing.com/img/left_03_m.jpg";
 imgs[6] = new Image();  imgs[6].src = "http://1000marketing.com/img/left_04.jpg";
 imgs[7] = new Image();  imgs[7].src = "http://1000marketing.com/img/left_04_m.jpg";
 imgs[8] = new Image();  imgs[8].src = "http://1000marketing.com/img/left_05.jpg";
 imgs[9] = new Image();  imgs[9].src = "http://1000marketing.com/img/left_05_m.jpg";
 imgs[10] = new Image();  imgs[10].src = "http://1000marketing.com/img/left_06.jpg";
 imgs[11] = new Image();  imgs[11].src = "http://1000marketing.com/img/left_06_m.jpg";
 imgs[12] = new Image();  imgs[12].src = "http://1000marketing.com/img/left_07.jpg";
 imgs[13] = new Image();  imgs[13].src = "http://1000marketing.com/img/left_07_m.jpg";
 //以下、
 // img[4] = new Image(); img[4].src = "画像URL";
 // img[5] = new Image(); img[5].src = "画像URL";
 //という風に番号の数字(img[数字])を一つずつ増やすことで
 //いくつでも画像を読み込んでおく事が出来ます。
}

function chgimg(id, imgname) {
 if(document.images) {
  if(imgs[imgname]) {
    document.images[id].src = imgs[imgname].src;
  }
  else {
    document.images[id].src = imgname;
  }
 }
}