Ajax not defined.

This is my code and I am trying to call remote function when somebody
click on add button after selecting something from select_tag. Please
tell me where I am wrong ? I am getting following error: Ajax not
defined.

<input type="button" value="< Add" class="button" onclick="<%=
remote_function(:url => {:controller => 'users', :action => 'add_line'})
%>" />

<%= select_tag 'available_line_id[]',options_for_select(customers),{:id
=> 'available_line_id',:multiple => true, :size => 13, :style => 'width:
225px;'} %>

Thanks,

Attachments:
http://www.ruby-forum.com/attachment/3475/new.html.erb

This is my code and I am trying to call remote function when somebody
click on add button after selecting something from select_tag. Please
tell me where I am wrong ? I am getting following error: Ajax not
defined.

Probably means that your page doesn't load the prototype javascript
library (which is the thing that adds the Ajax object). See
javascript_include_tag

Fred