.viewer {
  margin: 0 auto;
  width: 950px;
  height: 485px;
  text-align: left;
  overflow: hidden;
}

.viewer ul {
  width: 950px;
  height: 485px;
  text-align: left;
  overflow: hidden;
  position: relative;
}

.viewer ul li {
  top: 0;
  left: 0;
  width: 950px;
  height: 485px;
  display: none;
  position: absolute;
}

.viewer ul li img {
  border:none;
  display:block;
  margin:0 auto;
}