.viewer {
  margin: 0 auto;
  width: 100%;
  position: relative;
  overflow: hidden;
}
.viewer ul {
  width: 100%;
  overflow: hidden;
  position: relative;
}
.viewer ul li {
  top: 0;
  left: 0;
  width: 100%;
  position: absolute;
}
.viewer ul li img {
  width: 100%;
}

.viewer ul:after {
  content: ".";
  height: 0;
  clear: both;
  display: block;
  visibility: hidden;
}

.viewer ul {
  display: inline-block;
  overflow: hidden;
}