// JavaScript Document
var wall = new Array();

/* 使用する背景画像を好きなだけ記述 */
wall[0] = "img/bg-img/bg_idx-1a.jpg";
wall[1] = "img/bg-img/bg_idx-2a.jpg";
wall[2] = "img/bg-img/bg_idx-3a.jpg";

var rnd = Math.floor((Math.random() * 100)) % wall.length;
document.write('<style type="text/css">#wrapp-idx { background:url(' , wall[rnd] , ') no-repeat center; }</style>');