site/layouts/404.html

{{ define "main"}}
<div class="contain error-page">
  <h1>404 Page not found</h1>
  <ul>
    {{ range .Site.Menus.main }}
    <li>
      {{ $url := urls.Parse .URL }}
      {{ $baseurl := urls.Parse $.Site.Params.Baseurl }}
      <a
        href="{{ with .Page }}{{ .RelPermalink }}{{ else }}{{ .URL | relLangURL }}{{ end }}"
        {{ if ne $url.Host $baseurl.Host }}target="_blank"{{ end }}
      >
        {{ .Name }}
      </a>
    </li>
    {{ end }}
  </ul>
</div>
{{ end }}