var topimg_array=new Array(5);
for(i=0;i<topimg_array.length;i++){
topimg_array[i]=new Image; topimg_array[i].src="/top_img/top" + i + ".jpg";}
i=Math.floor(Math.random()*5);
document.write("<img src=\"" + topimg_array[i].src + "\" border=\"0\" width=\"900\" height=\"120\" alt=\"\" />");