<main>
  <div>
    This is an element centered with line-height hack.
  </div>
</main>

body {
  background: #40BDB7;
  font-size: 80%;
}

main {
  background: white;
  margin: 20px 0;
  padding: 40px;
}

main div {
  background: black;
  color: white;
  height: 100px;
  line-height: 100px;
  padding: 20px;
  width: 70%;
  white-space: nowrap;
  border-radius: 5px;
}