editable_header_pseudocode.rb

# Method 1: add an after filter to set the variable, use it in the application layout
PageController.class_eval do
  after_filter :set_header_quote, :only => [:show]
  
  private :set_header_quote
  def set_header_quote
    @header_quote = 'Some header quote'
  end
end

# in the layout
<div id="header"><%= @header_quote %></div>

# Method 2: add header_quote as a PagePart, then utilize it in either the application or layout
  # run in console to add the part to all pages
Page.all.each {|p| p.parts << PagePart.create(:title => 'header')}
  # configure ensure that all future pages created with the backend have the header 
  # (only when using the pnt_pages plugin or an upcomming version of the gem)
Page.class_eval do
  def self.default_page_parts
    ['body','side_body','header']
  end
end

# application (conditional required because not all actions assign a Page)
<% if @page.present? %>
  <div id="header"><%= @page['header'] %></div>
<% end %>

# shared/content_page
<div id="body_content">
 . . .
 <div id="header"><%= @page['header'] %></div>
</div>