function banner() {
};

banner = new banner();
number = 0;

// bannerArray
banner[number++] = "<a href='http://www.fetishcod.com/store/trample' target='_blank'><img src='images/banners/fc/trample-90x35.gif' border='0'></a>"

// keep adding items here...

increment = Math.floor(Math.random() * number);

document.write(banner[increment]);