AJAX Codeigniter problem

[eluser]Unknown[/eluser]
I have a main controller that prepares the view of my site then loads it.
I have one view and I want to load my content there via Jquery Ajax.
I use $.post or$('selector').load to get my content.

My problem is this:
if i post my Ajax request to the controller that loaded the view or any other controller in fact it works fine if the address is http://mywebsite.com but i get a 301 moved permanently if the address is http://www.mywebsite.com

is it a general Ajax problem? or a specific codeigniter?