#block3 {
  position: relative;
  display: inline-block;
  width: 100%;
}
#block3 a {
  position: absolute;
}
#block3 a:nth-of-type(1) {
  left: 15.5%;
  top: 22%;
  width: 22%;
  height: 78%;
}
#block3 a:nth-of-type(2) {
  left: 39%;
  top: 22%;
  width: 22%;
  height: 78%;
}
#block3 a:nth-of-type(3) {
  left: 63%;
  top: 22%;
  width: 22%;
  height: 78%;
}
#block3 a:hover {
  background: rgba(255,255,255,.3);
}