Edit in JSFiddle

<div class="without-x">
  <span></span>
</div>
<div class="with-x">
  x<span></span>
</div>
<div class="font-size-0">
  <span></span>
</div>

div {
  background-color: #ff00ff;
  margin-bottom: 10px;
}
span {
  display: inline-block;
}
.font-size-0 {
  font-size: 0px;
}