function dash_menu() {
    ...
    ...
    $menuitems['mytest/feed/feedbackid/'] = array(
    'type' => MENU_CALLBACK,
    'page callback' => 'dash_feedbackid_callback',
    'access callback' => 'user_is_logged_in',
    'access arguments' => array('access content'),
    );
   return $menuitems;

jQuery.ajax({
                type: 'POST',
                url: '/mytest/feed/feedbackid/',
                dataType: 'json',
                success: function(data){
                    alert('ok')
                },
                // Might want to use 'ui' instead of jQuery('#slider').
                data: 'slider_value=' + '1',
            });

POST http://localhost//mytest/feed/feedbackid/ 404 (Not Found)