body {
  margin: 0px;
  padding: 0px;
  width: 800px;
  height: 598px;
  background-color: #CCC;
  border: solid 2px #FFF;
}

#pic {
  display: none;
}

#pix img {
  position: absolute;
  top: 2px;
  left: 2px;
  width: 800px;
  height: 598px;
}

#pic_a {
  opacity: 0;
}

#pic_b {
  opacity: 1;
}

#pic_next {
  position: absolute;
  height: 44px;
  width: 44px;
  top: 279px;
  right: 20px;
  background-image: url('pix/pic_next.png');
}

#pic_next:hover {
  background-image: url('pix/pic_next_over.png');
}

#pic_prev {
  position: absolute;
  height: 44px;
  width: 44px;
  top: 279px;
  left: 20px;
  background-image: url('pix/pic_prev.png');
}

#pic_prev:hover {
  background-image: url('pix/pic_prev_over.png');
}