.aa {
  background:url(./img/10.gif) no-repeat;
  width:100px; height:20px;
  margin:0; padding:0;
  display:block;
}

.aa:hover {
  background:url(./img/11.gif) no-repeat;
}


.bb {
  background:url(./img/20.gif) no-repeat;
  width:100px; height:20px;
  margin:0; padding:0;
  display:block;
}

.bb:hover {
  background:url(./img/21.gif) no-repeat;
}

.cc {
  background:url(./img/30.gif) no-repeat;
  width:100px; height:20px;
  margin:0; padding:0;
  display:block;
}

.cc:hover {
  background:url(./img/31.gif) no-repeat;
}

.dd {
  background:url(./img/40.gif) no-repeat;
  width:100px; height:20px;
  margin:0; padding:0;
  display:block;
}

.dd:hover {
  background:url(./img/41.gif) no-repeat;
}

.ee {
  background:url(./img/50.gif) no-repeat;
  width:100px; height:20px;
  margin:0; padding:0;
  display:block;
}

.ee:hover {
  background:url(./img/51.gif) no-repeat;
}

.ff {
  background:url(./img/60.gif) no-repeat;
  width:100px; height:20px;
  margin:0; padding:0;
  display:block;
}

.ff:hover {
  background:url(./img/61.gif) no-repeat;
}