var banner=new Array()
banner[0]='<script src="http://ad.garantiarkadas.com/bannerhtml/banner.php?affiliateID=13788&bg=1&B=4"></script>'
banner[1]='<script src="http://mp3.rngfn.com/atakMp3.php?A=21931&B=4"></script>'

var hangisi=Math.floor(Math.random()*(banner.length))
document.write(banner[hangisi])