<!DOCTYPE html>
<link href="support/flexbox.css" rel="stylesheet">

<style>
.flexbox {
  background-color: lightgrey;
}
</style>

<div class='flexbox'>
  <!-- flex item: block child -->
  <div>block</div>
  <!-- flex item: anonymous block box around inline content -->
  anonymous item 2
  <!-- flex item: inline child -->
  <span>item 3</span>
</div>