app/views/labs/404.html.haml
.jumbotron.text-center
= title "Lab Not Found - 404 error", class: "text-danger"
%br
%p Unable to find any Lab matching the URL provided. Try searching or browse through the list of labs.
%br
= link_to t("views.header.labs"), labs_path, class: "btn btn-primary btn-lg"