views/404.erb
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title><%= title 'Error 404' %></title>
<link href="<%= prefix_url("assets/application.css") %>" rel="stylesheet">
</head>
<body>
<div class="container-fluid">
<div class="row-fluid text-info service-page">
<h1>404 <small>Page not found</small></h1>
<p class="lead">Sorry, this page is not available.</p>
<a href="/" class="btn btn-info">Back to home</a>
</div>
</div>
</body>
</html>