img = new Array();
img[0] = "common/images/visual_top01.jpg";
img[1] = "common/images/visual_top02.jpg";
img[2] = "common/images/visual_top03.jpg";
img[3] = "common/images/visual_top04.jpg";
n = Math.floor(Math.random()*img.length);
document.write("<img src='"+img[n]+"' border='0'>");