#button-credits{
  -moz-box-orient: horizontal;
  -moz-box-direction: reverse;
  list-style-image: url('chrome://BAS/skin/credits.png');
}

#button-credits[disabled="true"]{
  -moz-box-orient: horizontal;
  -moz-box-direction: reverse;
  list-style-image: url('chrome://BAS/skin/credits-disabled.png');
}
