var how_many_ads = 2;  
var now = new Date()  
var sec = now.getSeconds()  
var ad = sec % how_many_ads;  
ad +=1;  
if (ad==1) {  
document.write('<a href="http://www.mediup.co.kr/" target="_blank"><img src="/banner/468/mediup_3.gif" width="468" height="60" border="0"></a>')
}  
if (ad==2) {  
document.write('<a href="http://www.mediup.co.kr/" target="_blank"><img src="/banner/468/mediup_3.gif" width="468" height="60" border="0"></a>')
}