var how_many_ads = 2;
var now = new Date();
var sec = now.getSeconds();
var ad = sec % how_many_ads;
ad +=1;
if (ad==1) {
var msg4="<center><IFRAME src=http://www.biztrees.com/top.htm frameborder=0 width=468 height=60 scrolling=no></IFRAME><br></center>"
document.write(msg4)
}
if (ad==2) {
var msg4="<center><IFRAME src=http://www.biztrees.com/top1.htm frameborder=0 width=468 height=60 scrolling=no></IFRAME><br></center>"
document.write(msg4)
}