function banner(img_source,url,alt,chance) {
   this.img_source = img_source;
   this.url = url;
   this.alt = alt;
   this.chance = chance;
}
function display() {
   with (this) document.write("<A HREF=" + url + "><IMG SRC='" + img_source + "' WIDTH=365 HEIGHT=49 BORDER=0 ALT='" + alt + "'></A>");
}
banner.prototype.display = display;
banners = new Array();
banners[0] = new banner("banery/ticketpro.gif",
                        "http://www.ticketpro.pl target='_blank'",
                        "TicketPro", 
                        10);
banners[1] = new banner("banery/dekompresja.gif",
                        "http://www.dekompresja.com.pl target='_blank'",
                        "Dekompresja", 
                        10);
banners[2] = new banner("banery/almatur.gif",
                        "http://www.e-almatur.pl target='_blank'",
                        "Biuro Podróży Almatur", 
                        10);
banners[3] = new banner("banery/eventim.gif",
                        "http://www.eventim.pl target='_blank'",
                        "Eventim", 
                        10);
banners[4] = new banner("banery/cgm.gif",
                        "http://www.cgm.pl target='_blank'",
                        "CGM OK", 
                        10);
banners[5] = new banner("banery/student.jpg",
                        "http://www.student.lodz.pl target='_blank'",
                        "Portal studencki", 
                        10);
banners[6] = new banner("banery/pasja.jpg",
                        "http://www.pasja.media.pl target='_blank'",
                        "Pasja - Agencja Artystyczno-Reklamowa", 
                        10);
banners[7] = new banner("banery/komok.jpg",
                        "http://www.komok.pl target='_blank'",
                        "KomoK", 
                        10);
banners[8] = new banner("banery/wytwornia.jpg",
                        "http://www.wytwornia.pl target='_blank'",
                        "Klub Wytwórnia", 
                        10);
banners[9] = new banner("banery/bileteria.jpg",
                        "http://www.bileteria.pl target='_blank'",
                        "Bileteria", 
                        10);


sum_of_all_chances = 0;
for (i = 0; i < banners.length; i++) {
   sum_of_all_chances += banners[i].chance;
}
function display_banner() {
   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].img_source + "' WIDTH=365 HEIGHT=49 BORDER=0 ALT='" + banners[i].alt + "'></A>");
         return banners[i];
         break;
      }
   }
}