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=222 HEIGHT=222 BORDER=0 ALT='" + alt + "'></A>");
}
banner.prototype.dispBanner = dispBanner;
banners = new Array();
banners[0] = new banner("./images/scritta1.jpg", "http://www.cavalierideltratturo.it", "",20);
banners[1] = new banner("./images/scritta2.jpg", "http://www.cavalierideltratturo.it", "",20)
banners[2] = new banner("./images/scritta3.jpg", "http://www.cavalierideltratturo.it", "",20)
banners[3] = new banner("./images/scritta4.jpg", "http://www.cavalierideltratturo.it", "",20)
banners[4] = new banner("./images/scritta5.jpg", "http://www.cavalierideltratturo.it", "",20)
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=222 HEIGHT=222 BORDER=0 ALT='" + banners[i].alt + "'></A>");
return banners[i];
break;
      }
   }
}