function banner() {
};

banner = new banner();
number = 0;

// bannerArray
banner[number++] = "<a href='downloads_wallpapers_ganpati.htm'><img border='0' src='random-link/wallpaper_ganpati6.jpg'></a>"
banner[number++] = "<a href='marathi_wallpapers.htm'><img border='0' src='random-link/marathi-wallpapers.jpg'></a>"
banner[number++] = "<a href='downloads_wallpapers_ganpati.htm'><img border='0' src='random-link/wallpaper_ganpati6.jpg'></a>"
banner[number++] = "<a href='marathi_wallpapers.htm'><img border='0' src='random-link/marathi-wallpapers.jpg'></a>"
// keep adding items here...

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

document.write(banner[increment]);