class="error">Firefox seems to have a rounding error.</p>
<table style="width: calc(400px + 6 * 8px)" data-expected-width=448>
  <tr>
    <td colspan=2 style="width:40%" data-expected-width=168><div style="width:40px"></div></td>
    <td colspan=2 style="width:20%" data-expected-width=88><div style="width:20px"></div></td>
    <td style="width:40%;box-sizing:border-box" data-expected-width=160><div style="width:40px"></div></td>
  </tr>
  <tr>
    <td data-expected-width=80>Auto</td>
    <td data-expected-w