function random(){

url = new Array(4); 
img = new Array(url.length); 

i = Math.floor(Math.random( ) * url.length);

url[0]="広告先";
img[0]="http://www.dreaming-of-hotelbabylon.jp/design/funnyface/image/visual1.jpg";

url[1]="広告先";
img[1]="http://www.dreaming-of-hotelbabylon.jp/design/funnyface/image/visual2.jpg";

url[2]="広告先";
img[2]="http://www.dreaming-of-hotelbabylon.jp/design/funnyface/image/visual3.jpg";

url[3]="広告先";
img[3]="http://www.dreaming-of-hotelbabylon.jp/design/funnyface/image/visual4.jpg";

/*これ以降は、3,4,5と数字を増やしてください。*/

document.write('<img src="'+img[i]+'" alt="" width="900" height="400" />');

}