app/views/layouts/login.html.erb
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1">
<%= favicon_link_tag 'favicon.ico' %>
<%= favicon_link_tag 'apple-touch-icon.png', :rel => 'apple-touch-icon', :type => 'image/png' %>
<title><%= @page_title -%></title>
<%= stylesheet_link_tag @user_theme %>
</head>
<body class="bootstrap">
<%= yield %>
</body>
</html>