How the use Ajax with Codeigniter?

[eluser]ytsejam[/eluser]
Hello,
I am a newbie developer and I am writing a website with codeigniter. It is really fun about anything I coded. Now my problem is , I use MY_Controller.

Code:

function render_page($view) {
    if( ! $this->input->is_ajax_request() )
    {
      //do this to don't repeat in all controllers...
      $this->load->view('templates/header', $this->data);
      //menu_data must contain the structure of the menu...
      //you can populate it from database or helper
    }
    $this->load->view($view, $this->data);
    if( ! $this->input->is_ajax_request() )
    {
     $this->load->view('templates/menu');
     $this->load->view('templates/footer', $this->data);
    }
  }

My home.php/about.php works without any problems. I want only <div id="content"> part to change when i click about or other links in the navigation menu.
How can i enable the ajax?
Thank you .