div.meter-element {
  display: inline-block;
  height: 1em;
  width: 5em;
  vertical-align: -0.2em;

  background-color: grey;
}

div.meter-element.vertical {
  height: 5em;
  width: 1em;
}

div.meter-bar {
  float: none ! important;

  height: 100%;
  /*
   * We can't apply the following style to the reference because it will have
   * underisable effectes:
   * width: 100%;
   */

  background-color: green;
}

meter, meter::-moz-meter-bar, div.meter-element, div.meter-bar {
  -moz-appearance: none;
}

meter {
  background: grey;
}

meter::-moz-meter-bar {
  background: green;
}