function random_photo01(){
   var imglist = new Array(
      "toppic/top2/01.jpg",
      "toppic/top2/02.jpg",
      "toppic/top2/03.jpg",
      "toppic/top2/04.jpg" );
   var selectnum = Math.floor((Math.random() * 100)) % imglist.length;
   var output = "<img src=" + imglist[selectnum]+">";
   document.write(output);
}