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

@-moz-document domain("kottke.org") {

  /* This is my first time posting to userstyles.org, so I'm not sure if you *just* need the following bit... */

  #t, #r, #b, #l, #tl, #tr, #bl, #br {
    display: none !important;
  }

}