var ilosc=2;
var losowa=Math.floor(ilosc*Math.random());
var baner="";

if(losowa==0) {
baner="<script src='http://www.weben1.com/Banner/Show?b=113&a=442'></script>";

}else

if(losowa==1) {
baner="";

}else;

document.write(baner);