@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document domain(mixi.jp) {
  img[src*="ads.mixi.jp"],
  embed[src*="ads.mixi.jp"],
  iframe[src*="ads.mixi.jp"],
  #adBanner,
  #prSepecial,
  #prContentsArea,
  #contentMatch,
  .adBanner
  {
    display: none !important;
  }
}