var imglist = new Array(
  "img/index_img1.jpg",
  "img/index_img2.jpg",
  "img/index_img3.jpg",
  "img/index_img4.jpg",
  "img/index_img5.jpg",
  "img/index_img6.jpg",
  "img/index_img7.jpg",
  "img/index_img8.jpg",
  "img/index_img9.jpg",
  "img/index_img10.jpg" );
 
var selectnum = Math.floor((Math.random() * 100)) % imglist.length;
document.write("<img src=" + imglist[selectnum] + " alt=トップ絵はランダムで変わるで★>");
//document.write(output);