##new.rhtml

  <label name=center[country_id]>Country</label>

   <select name="center[country_id]" id="center_country_id">
     <option value="">-- Select Country --</option>
 	 <% @countries.each do |country| %>
	   <option value=<%= country.id %>><%= country.name %>
	 <% end %>
   </select>

   <div id="center_state_container">
               <%= render :partial => 'select_state'%></p>
   </div>

   <%= observe_field("center_country_id",
			    :frequency => 1,
			    :update => "center_state_container",
	                    :url => {:controller => 'center', :action =>'filtered_state_select',:method=>'post'},
	                    :with => "'country_id=' + escape(value)",
                            :on=> 'click')%>

   <br>
   <center><%= submit_tag "Submit" %></center>



##CenterController.rb

  def filtered_state_select
    @states = State.find_all_by_country_id(params["country_id"])
    render :partial => 'select_state'
  end

  def filtered_city_select
    @cities = City.find_all_by_state_id(params["state_id"])
    render :partial => 'select_city'
  end


##_select_state.rhtml [partial]

<% if @states %>
  <label name=center[state_id]>States:</label>
    <select name="center[state_id]" id="center_state_id">
      <option value="">-- Select State --</option>

	 <% @states.each do |state| %>
	   <option value=<%= state.id %>><%= state.name %>
	 <% end %>

    </select>
<% end %>

<div id="center_city_container">
  <%= render :partial => 'select_city'%></p>
</div>

<%= observe_field("center_state_id",
 			:frequency => 1,
			:update => "center_city_container",
	                :url => {:controller => 'center', :action => 'filtered_city_select',:method=>'post'},
	                :with => "'state_id=' + escape(value)",
			:on=> 'click')%>


<br>


##_select_city.rhtml  [partial]


<br>

<% if @cities %>
<label name=center[city_id]>City:</label>
<select name="center[city_id]" id="center_city_id">
     <option value="">-- Select City --</option>

	<% @cities.each do |city| %>
	  <option value=<%= city.id %>><%= city.name %>
	<% end %>

</select>
<% end %>