var how_many_ads = 3;  
var now = new Date()  
var sec = now.getSeconds()  
var ad = sec % how_many_ads;  
ad +=1;  
if (ad==1) {   
url="#";  
alt="";  
banner="images/images/1da.jpg";  
width="784";  
height="439";  
}  
if (ad==2) {   
url="#";  
alt="";  
banner="images/images/2da.jpg";  
width="784";  
height="439";  
}  
if (ad==3) {   
url="#";  
alt="";  
banner="images/images/1da.jpg";  
width="784";  
height="439";  
}     
document.write('<a href="' + url + '" target="_blank">');  
document.write('<img src="' + banner + '" width=')  
document.write(width + ' height=' + height + ' ');  
document.write('alt="' + alt + '" border=0>');