a #logo {
  background-image : url("/images/logo_off.gif");
  background-repeat: no-repeat;
  border : 0px solid red;
  height : 50px;
  margin-left : auto;
  margin-right : auto;
  text-align : center;
  width : 50px;
  z-index : 6;
}

a:active #logo  {
  background-image : url("/images/logo_here.gif");
}

a:active:hover #logo {
  background-image : url("/images/logo_on.gif");
}

a:hover #logo {
  background-image : url("/images/logo_on.gif");
}

a:link #logo {
  background-image : url("/images/logo_off.gif");
}

a:visited #logo {
  background-image : url("/images/logo_off.gif");
}

a:visited:hover #logo {
  background-image : url("/images/logo_on.gif");
}