imgURL  = new Array();
imgURL[0]  = "photo/top_img/l1.jpg";
imgURL[1]  = "photo/top_img/l2.jpg";
imgURL[2]  = "photo/top_img/l3.jpg";
imgURL[3]  = "photo/top_img/l4.jpg";
imgURL[4]  = "photo/top_img/l5.jpg";
imgURL[5]  = "photo/top_img/l6.jpg";
imgURL[6]  = "photo/top_img/l7.jpg";

n = Math.floor(Math.random()*imgURL.length);
document.write("<img src='"+imgURL[n]+"' border='0' width='820' height='120'>");