Skip link style

background is defined twice. is this some kind of trick or is it just an error?

#skip-link a,
#skip-link a:link,
#skip-link a:visited {
  background: #444;
  background: rgba(0, 0, 0, 0.6);
  color: #fff;
  display: block;
  line-height: 2;
  padding: 0;
  text-align: center;
  text-decoration: none;
  -khtml-border-radius: 0 0 10px 10px;
  -moz-border-radius: 0 0 10px 10px;
  -webkit-border-top-left-radius: 0;
  -webkit-border-top-right-radius: 0;
  -webkit-border-bottom-left-radius: 10px;
  -webkit-border-bottom-right-radius: 10px;
  border-radius: 0 0 10px 10px;
}