/*
https://stackoverflow.com/questions/1495407/maintain-the-aspect-ratio-of-a-div-with-css
usage: <div class="aspect_ratio_4_3"><div>my stuff</div></div>
*/

div.aspect_ratio_4_3 {
  width: 100%;
  padding-bottom: 75%;
  position: relative;
}

div.aspect_ratio_4_3 > div {
  position: absolute;
  top: 0; bottom: 0; left: 0; right: 0;
}