Seaches with ajax

Rails
1

I have problems using ajax in a search field.
In view/layouts I have main.html.erb with code:

<?xml version="1.0" encoding="UTF-8"?> Consegna sacchetti <%= stylesheet_link_tag 'scaffold' %> <%= javascript_include_tag :defaults %>

…

in application.controller I have put layout “main”.

under view/sacchetti I have index.html.erb for sacchetti_controller:

<% form_tag'javascript:void(0)' do %>

<%= label_tag :search, 'Nominativo:' %> <%= text_field_tag :search, params[:search] %> <%= image_tag("indicator.gif", :id => "spinner", :style => "display: none;") %>

<% end %> <%= observe_field(:search, :frequency => 0.5, :update => :search_hits, :loading => "Element.show('spinner')", :complete => "Element.hide('spinner')", :url => {:action => :list, :method => :get}, :with => "'search=' + escape(value)")%>
<%= render :partial=>'rusers_list' %>

observe_files seems don’t work, with firebug I see no ajax requests.
What I’ve missed?

p.s. sorry for my bad english