var wall = new Array();

/* 使用する背景画像を好きなだけ記述 */
wall[0] = "./ex/img/bg_2nd_001.jpg";
wall[1] = "./ex/img/bg_2nd_002.jpg";
wall[2] = "./ex/img/bg_2nd_003.jpg";
wall[3] = "./ex/img/bg_2nd_004.jpg";
wall[4] = "./ex/img/bg_2nd_005.jpg";
wall[5] = "./ex/img/bg_2nd_006.jpg";
wall[6] = "./ex/img/bg_2nd_007.jpg";
wall[7] = "./ex/img/bg_2nd_008.jpg";


var rnd = Math.floor((Math.random() * 100)) % wall.length;
document.write('<style type="text/css">#head {background:url(' , wall[rnd] , ') no-repeat 490px -40px;}</style>');