var banner_count = 3;

// inject a banner into an element
function nntpchan_inject_banners(elem, prefix) {
  var n = Math.floor(Math.random() * banner_count);
  var banner = prefix + "static/banner_"+n+".jpg";
  var e = document.createElement("img");
  e.src = banner;
  e.id = "nntpchan_banner";
  elem.appendChild(e);
}