img = new Array();

img[0] = "img/img_top0.jpg";
img[1] = "img/img_top1.jpg";
img[2] = "img/img_top2.jpg";

var n = Math.floor(Math.random() * img.length);

document.write("<h1><img src='" + img[n] + "' alt='ジェコスは日本の街づくりを基礎から支えています' width='900' height='241' class='forPrint' /></h1>");