Sending form with AJAX - ampersand problem

<?
            include("/fckeditor/fckeditor.php") ;
            $oFCKeditor = new FCKeditor('input1') ;
            $oFCKeditor -> BasePath = '/fckeditor/';
            $oFCKeditor -> Value = 'Default text in editor';
            $oFCKeditor -> Create() ;
            ?>

            <input type="hidden" name="co" value="<?echo $kategoria?>" id="co">