jmp = new Array();
img = new Array();

jmp[0] = "/daimei/";
jmp[1] = "/genba/";

img[0] = "./top/images/top/bnr_daimei.jpg";
img[1] = "./top/images/top/bnr_iryo.jpg";

n = Math.floor(Math.random()*jmp.length);

document.write("<a href='"+jmp[n]+"'>" + "<img src='"+img[n]+"' border='0'>" + "</a>");