user-style.css

@-moz-document domain("expressjs.com") {
  * {
    text-shadow: none !important;
  }
  body {
    background: #aaa !important;
  }
  a {
    color: #07a !important;
  }
  a:visited {
    color: #080 !important;
  }
  code, pre {
    background: #d8d8d8 !important;
  }
}