#block4 {
  position: relative;
  display: inline-block;
  width: 100%;
}
#block4 a {
  position: absolute;
}
#block4 a:nth-of-type(1) {
  left: 6%;
  top: 45%;
  width: 17%;
  height: 40%;
}
#block4 a:nth-of-type(2) {
  left: 24%;
  top: 45%;
  width: 17%;
  height: 40%;
}
#block4 a:nth-of-type(3) {
  left: 42%;
  top: 45%;
  width: 17%;
  height: 40%;
}
#block4 a:nth-of-type(4) {
  left: 60%;
  top: 45%;
  width: 17%;
  height: 40%;
}
#block4 a:hover {
  background: rgba(255,255,255,.3);
}