jumpURL = new Array(); imgURL = new Array();
jumpURL[0] = "http://www.jyouhou.ne.jp/"; 
jumpURL[1] = "http://www.info-cash.com/icswt.asp?FID=shun1y"; 

imgURL[0] = "http://www.jyouhou.ne.jp/banner.gif"; 
imgURL[1] = "http://www.info-cash.com/bana/info_bana08.gif"; 

n = Math.floor(Math.random()*jumpURL.length); 
document.write("<a href='"+jumpURL[n]+"'>"); 
document.write("<img src='"+imgURL[n]+"'>"); 
document.write("</a>");