.aa {
  background:url(./img/1_00.gif) no-repeat;
  width:183px; height:20px;
  margin:0; padding:0;
  display:block;
}

.aa:hover {
  background:url(./img/1_01.gif) no-repeat;
}

.bb {
  background:url(./img/2_00.gif) no-repeat;
  width:183px; height:20px;
  margin:0; padding:0;
  display:block;
}

.bb:hover {
  background:url(./img/2_01.gif) no-repeat;
}

.cc {
  background:url(./img/3_00.gif) no-repeat;
  width:183px; height:20px;
  margin:0; padding:0;
  display:block;
}

.cc:hover {
  background:url(./img/3_01.gif) no-repeat;
}

.dd {
  background:url(./img/4_00.gif) no-repeat;
  width:183px; height:20px;
  margin:0; padding:0;
  display:block;
}

.dd:hover {
  background:url(./img/4_01.gif) no-repeat;
}