hugo-coder/layouts/partials/404.html

<section class="container centered">
  <div class="error">
    <h1>404</h1>
    <h2>{{ i18n "page_not_found" }}</h2>
    <p>{{ i18n "page_does_not_exist" }}<br />{{ i18n "head_back" .Site.BaseURL | safeHTML }}</p>
  </div>
</section>