What does "*left: 0%" do?

Is this a bug or for a special browser? It doesn't look like the IE6 star hack... any chance to get a comment on this lines in lightbox_alt.css and lightbox.css, please?

#loading {
  height: 25%;
  width: 100%;
  text-align: center;
  line-height: 0;
  position: absolute;
  top: 40%;
  left: 45%;
  *left: 0%;
}