<!DOCTYPE html>
<!--
 | For inline non-replaced elements, the box used for alignment is the box whose
 | height is the "line-height" (containing the box's glyphs and the half-leading
 | on each side).
 |   https://www.w3.org/TR/CSS21/visudet.html#propdef-vertical-align
 -->
<html>
<head>
  <style>
    body {
      margin: 0px;
      font-family: Roboto;
      font-size: 100px;
      font-weight: bold;
      line-height: 300px;
    }
    .baseline-marker {
      background-color: #e0e0e0;
      display: inline-block;
      height: 5px;
      width: 100px;
    }
    .with-align-top {
      vertical-align: top;
    }
    .with-align-bottom {
      /*vertical-align: bottom;*/
    }
    .with-normal-line-height {
      line-height: normal;
    }
  </style>
</head>
<body>
  <div class="baseline-marker"></div>
  <span class="with-align-top">b</span>
  <span class="with-align-bottom">q</span>
  <span class="with-normal-line-height with-align-top">b</span>
  <span class="with-normal-line-height with-align-bottom">q</span>
</body>
</html>