var imglist = new Array(
      "http://2wanhappy.com/wp-content/themes/default/images/main1.jpg",
      "http://2wanhappy.com/wp-content/themes/default/images/main2.jpg",
      "http://2wanhappy.com/wp-content/themes/default/images/main3.jpg",
      "http://2wanhappy.com/wp-content/themes/default/images/main4.jpg");
   var selectnum = Math.floor((Math.random() * 100)) % imglist.length;
   var output = "<img src=" + imglist[selectnum] + " border='0'>";
   document.write(output);