<title>Ambiguous line width</title>

<div style="background: yellow; width: 10em; height: 10em; position: relative">
  <div style="position: absolute; top: 0; left: 0; height: 2em; width: 2em; background: blue"></div>
  <div style="position: absolute; top: 2em; left: 0; height: 2em; width: 5em; background: aqua"></div>

  <span style="position: absolute; top: 0; left: 2em; height: 1em; width: 3em; background: maroon; vertical-align: bottom"></span>
  <span style="position: absolute; top: 1em; left: 5em; height: 3em; width: 5em; background: maroon; vertical-align: bottom"></span>

</div>