docs/en/_templates/404.html

{% extends "layout.html" %}

{% block body %}

<h1>Page Not Found</h1>
<p>
  The page you are looking for cannot be found.
</p>
<p>
  If you just switched documentation versions, it is likely that the page you were on is moved. You can look for it in
  the content table left, or go to <a href="{{ pathto(root_doc) }}">the homepage</a>.
</p>
<p>
  If you cannot find documentation you want, please <a
    href="https://github.com/open-mmlab/mmaction2/issues/new/choose">open an issue</a> to tell us!
</p>

{% endblock %}