
  descent-override: 50%;
}

.target {
  font: 20px Ahem;
  color: green;
  position: absolute;
  top: 10px;
  left: 10px;
}

.top-aligned {
  display: inline-block;
  background-color: green;
  vertical-align: top;
  width: 1em;
  height: 1em; /* Same as the overridden ascent */
}

.bottom-aligned {
  display: inline-block;
  background-color: green;
  vertical-align: bottom;
  width: 1em;
  height: 0.5em; /* Same as the overridden descent */
}

</style>
<div class="target">
  <span class="top-aligned"></s