var NumberOfAds = 21;
var now = new Date()
var sec = now.getSeconds()
var AdNumber = sec % NumberOfAds;
AdNumber +=1;
if (AdNumber==1)  Graphic="../images/radioimages/1.jpg";
if (AdNumber==2)  Graphic="../images/radioimages/2.jpg";
if (AdNumber==3)  Graphic="../images/radioimages/3.jpg";
if (AdNumber==4)  Graphic="../images/radioimages/4.jpg";
if (AdNumber==5)  Graphic="../images/radioimages/5.jpg";
if (AdNumber==6)  Graphic="../images/radioimages/6.jpg";
if (AdNumber==7)  Graphic="../images/radioimages/7.jpg";
if (AdNumber==8)  Graphic="../images/radioimages/8.jpg";
if (AdNumber==9)  Graphic="../images/radioimages/9.jpg";
if (AdNumber==10)  Graphic="../images/radioimages/10.jpg";
if (AdNumber==11)  Graphic="../images/radioimages/11.jpg";
if (AdNumber==12)  Graphic="../images/radioimages/12.jpg";
if (AdNumber==13)  Graphic="../images/radioimages/13.jpg";
if (AdNumber==14)  Graphic="../images/radioimages/14.jpg";
if (AdNumber==15)  Graphic="../images/radioimages/15.jpg";
if (AdNumber==16)  Graphic="../images/radioimages/16.jpg";
if (AdNumber==17)  Graphic="../images/radioimages/17.jpg";
if (AdNumber==18)  Graphic="../images/radioimages/18.jpg";
if (AdNumber==19)  Graphic="../images/radioimages/19.jpg";
if (AdNumber==20)  Graphic="../images/radioimages/20.jpg";
if (AdNumber==21)  Graphic="../images/radioimages/21.jpg";
document.write('<IMG SRC="' + Graphic + '" WIDTH=180 HEIGHT=125 BORDER=0 ALT="Small radio">')