<!DOCTYPE html>
<meta charset="utf-8">
<link rel="author" title="David Shin" href="mailto:dshin@mozilla.com">
<link rel="author" href="https://mozilla.org" title="Mozilla">
<style>
  body { margin: 0; }
  .cb {
    position: relative;
    inline-size: 45px;
    block-size: 40px;
    background: lightblue;
    border: solid gray;
    border-width: 1px 2px 3px 4px;
    float: left;
    margin-right: 5px;
  }
  .parent {
    inline-size: 35px;
    block-size: 30px;
    background: orange;
  }
  .abspos {
    i