<title>Ambiguous line width</title>

<div style="background: yellow; width: 10em; height: 10em; line-height: 1; font-family: sans-serif;">
  <div style="float: left; height: 0.5em; width: 1em; background: blue"></div>
  <div style="float: left; height: 2em; width: 10em; background: aqua"></div>

  <span style="display:inline-block; height: 1em; width: 4em; background: maroon; vertical-align: bottom"></span>

</div>