<!DOCTYPE html>
<!-- https://github.com/servo/servo/issues/9306 -->
<style>
  body {
    margin: 0;
  }

  .green {
    background: #0F0;
    height: 40px;
    width: 400px;
    top: 40px;
    left: 50%;
    margin-left: -300px;
    position: absolute;
    padding: 0px 100px;
  }

  .red {
    background: #F00;
    position: absolute;
    right: 0;
  }

</style>

<div class="green">
  <span class="red">x</span>
</div>