div.screenshot {
  width: 100%;
  text-align: center;
}

.screenshot img {
  box-shadow: 2px 2px 15px #202020;
  margin-top: 0.5em;
  margin-bottom: 2.0em;
}

div.prev {
    width: 50%;
    float: left;
    text-align: left;
}
div.next {
    width: 50%;
    float: right;
    text-align: right;
}
div.navlinks {
  width: 550px;
  margin-left: auto;
  margin-right: auto;
}

li img {
   vertical-align: middle;
}