%= stylesheet begin
  #header {
    margin-bottom:10px;
    border-bottom:1px solid black;
    height:40px;
  }

  #header li{
    float:left;
    padding: 10px 20px;
  }
% end
<div id="header">
  <ul>
    <li><a href="<%= url_for('/') %>">Home</a></li>
    <li><a href="<%= url_for("/$user") %>"><%= $user %></a></li>
    <li><a href="<%= url_for("/new") %>">Create a new repo</a></li>
    <li><a href="<%= url_for("/setting/profile") %>">Account setting</a></li>
    <li><a href="<%= url_for("/logout") %>">Sign out</a></li>
  </ul>
</div>
<div style="clear:both"/>