Pages controller action:

  # GET /pages/1/edit
  def edit
    @page = Page.find(params[:id])
  end

edit.js.rjs:
page.replace_html('page', :partial => 'edit_page', :object => @page)


edit_page.html.erb:
hello

show.html.erb:
<%= link_to_remote image_tag("edit.png"), :update => "page",
      :url => edit_page_path(@page), :method => :get %>

    <div id="page">
      <h2 class="title"><%=h @page.title %></h2>
      <div class="inner">
        <p>
          <%= @page.body %>
        </p>
      </div>
    </div>