_content/tour/static/partials/notfound.html

<div class="wrapper">
    <div class="container">

        <div class="page-header">
            <h1>Page not found</h1>
        </div>

        <p>The page you requested is not part of the tour.</p>

        <p><a href="/tour/list">Return to the table of contents</a>.</p>

    </div>
</div>