title: Rationale behind font sizes in bootstrap
body: <p>Here are the header sizes from <code>bootstrap.css</code>:</p>
  
  <pre><code>h1 {
    font-size: 38.5px;
  }
  
  h2 {
    font-size: 31.5px;
  }
  
  h3 {
    font-size: 24.5px;
  }
  </code></pre>
  
  <p>I was surprised by the fact that these sizes are fractional (half-integers), which suggests that their precision is at least <code>0.25px</code> (less than 1%).</p>
  
  <p>How do web designers arrive at such sizes? Are they obtained by some scientific process, some calculation perhaps? Or do people simply stare at their site, playing with sizes until it feels right? How can a designer convince his teammate that it really ought to be <code>31.5px</code> and not just <code>31px</code>?</p>