function banner(imgSource,url,alt,chance) {
this.imgSource = imgSource;
this.url = url;
this.alt = alt;
this.chance = chance;
}
function dispBanner() {
with (this) document.write("<A HREF=" + url + "><IMG SRC='" + imgSource + "' WIDTH=120 HEIGHT=180 BORDER=0 ALT='" + alt + "'></A>");
}
banner.prototype.dispBanner = dispBanner;
banners = new Array();
banners[0] = new banner("/images/ads/yoga.jpg",
                        "http://hrih.net/cgi-bin/shop/item.cgi?Operation=ItemLookup&ItemId=0970700601",
                        "A Manual for Students, Teachers, and Practitioners, Anatomy of Hatha Yoga",
                        10);
banners[1] = new banner("/images/ads/yogafr.gif",
                        "http://yoga.normandie.free.fr/",
                        "Yoga Normandie",
                        10);
banners[2] = new banner("/images/ads/ysp.jpg",
                        "http://hrih.net/cgi-bin/shop/item.cgi?Operation=ItemLookup&ItemId=8121504244",
                        "Patanjali's Yoga Sutras",
                        10);
sum_of_all_chances = 0;
for (i = 0; i < banners.length; i++) {
sum_of_all_chances += banners[i].chance;
}
function randomBanner() {
chance_limit = 0;
randomly_selected_chance = Math.round((sum_of_all_chances - 1) * Math.random()) + 1;
for (i = 0; i < banners.length; i++) {
chance_limit += banners[i].chance;
if (randomly_selected_chance <= chance_limit) {
document.write("<A HREF=" + banners[i].url + "><IMG SRC='" + banners[i].imgSource + "' WIDTH=120 HEIGHT=180 BORDER=0 ALT='" + banners[i].alt + "'></A>");
return banners[i];
break;
      }
   }
}