Header height

<header data-kit-site="header">
  <a href="../opening/"><span data-kit-mark aria-hidden="true">k</span><span data-kit-wordmark>kit</span></a>
  <nav aria-label="Site">
    <a href="../steps/">Product</a>
    <a href="../plans/">Pricing</a>
    <a href="../questions/">Questions</a>
  </nav>
  <details>
    <summary>Menu</summary>
    <nav aria-label="Site">
      <a href="../steps/">Product</a>
      <a href="../plans/">Pricing</a>
      <a href="../questions/">Questions</a>
      <a href="../action/">Log in</a>
    </nav>
  </details>
  <div data-kit-site-part="actions">
    <a href="../action/">Log in</a>
    <a data-kit-site-action="primary" href="../opening/">Start free</a>
  </div>
</header>
<main>
  <section data-kit-site="feature">
    <div>
      <hgroup>
        <p>Payment</p>
        <h2>Every invoice knows who still owes</h2>
      </hgroup>
      <p>Each booking raises its invoice, and a reminder goes to the hirer before the hire date.</p>
    </div>
  </section>
</main>