the form submission URL as the user might just have tried to change
it in which case the one in the user object will be the new one.
<h2>Edit details:</h2>
<%= error_messages_for 'user' %>
-<% form_tag :controller => 'user', :action => 'edit', :display_name => @user.display_name do %>
+<% form_tag :controller => 'user', :action => 'edit', :display_name => User.find(@user.id).display_name do %>
<table>
<tr><td>display name</td><td><%= text_field :user, :display_name, :value => @user.display_name %></td></tr>
<tr><td valign="top">description</td><td><%= text_area :user, :description, :value => @user.description %></td></tr>