app/views/common/errors/400.html.erb
<div class="uk-width-1-1">
<div class="uk-container">
<h1 class="uk-margin-medium uk-text-center uk-text-warning">400 Bad Request</h1>
<p class="uk-text-large uk-text-warning">不正なアクセスです</p>
<%= link_to '開催履歴へ移動する', events_path, class: 'uk-button uk-button-primary' %>
</div>
</div>