#slideshow {
  position: relative;
  float:left;
  width: 500px;
  height: 215px;
}

#slideshow_big {
  position: relative;
  float:left;
  width: 850px;
  height: 215px;
}

#slideshow div {
  position: absolute;
  top: 0;
  left: 0;
}

#slideshow_big div {
  position: absolute;
  top: 0;
  left: 0;
}