app/views/shared/_header.html.erb
<% cache("views/shared/header", :expires_in => 1.hour) { %>
<div class='header bar'>
<%= link_to image_tag("logo.png", :class => "logo"), root_path %>
<div class="treble_clef"></div>
<%= render :partial => "shared/external/github_fork_me" %>
</div>
<% } %>