function banner() {
};

banner = new banner();
number = 0;

// bannerArray
banner[number++] = "<a href=\"http://www.andorraprincipat.com/cat/banner_hotel.htm\" target=\"_self\"><img src='http://www.andorraprincipat.com/banner/hoteleria/banner_hoteleria.gif' width='419' height='62' border='0'></a>"
// keep adding items here...

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