app/views/errors/not_found.html.erb
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>404 - <%= t('not_found.title') %> - <%= t('cm-central') %></title>
<%= favicon_link_tag "favicon.ico" %>
<%= stylesheet_link_tag :application %>
</head>
<body class="NotFound">
<div class="NotFound__container">
<h2 class="NotFound__title">404</h2>
<h3 class="NotFound__description"><%= t('not_found.description') %></h3>
<%= link_to t('back'), request.referer || root_path, class: "NotFound__link" %>
</div>
</body>
</html>