.centered-btns_nav {
  z-index: 2;
  position:absolute;
  -webkit-tap-highlight-color: rgba(0,0,0,0);
  top: 160px;
  left: 0;
  opacity: 0.7;
  text-indent: -9999px;
  overflow:hidden;
  text-decoration: none;
  height: 45px;
  width: 45px;
  background: transparent url("themes.gif") no-repeat left top;
  margin-top: -45px;
  }

.centered-btns_nav:hover {
  opacity: 1.0;
  }

.centered-btns_nav.next {
  left: 100%;
  background-position: right top;
  right: 0;
  }
  
  .centered-btns_nav:focus{
  outline: none;
  }