Template:Infobox/styles.css

.infobox {
  float: right;
  clear: right;
  margin: 1em;
  width: 300px;
  max-width: 100%;
}

@media (max-width: 640px) {
  .infobox {
    float: none;
    width: auto;
    margin: 1em 0;
  }
}