app/views/layouts/tail/application.html.erb
<!DOCTYPE html>
<html>
<head>
<title><%= content_for :title %></title>
<%= stylesheet_link_tag "tail/application", media: "all" %>
<%= javascript_include_tag "tail/application" %>
<%= csrf_meta_tags %>
</head>
<body>
<%= yield %>
</body>
</html>