Jquery Ajax Request return forbidden (403) in cakePHP project

Question

EDIT 2

I still need help, as the error still isn\'t fixed. Below I have added a link to a screenshot of what .ajaxError() does throw:

http://i.i

Answer 1

I have now changed my jQuery Ajax-Call that looks like following

    $.ajax({
        url: '/metas/saveMetas',
        data: {
            "model": model,
            "f_key": f_key,
            "pagetitle": pagetitle,
            "keywords": keywords,
            "description": description,
            "niceurl": niceurl
        },
        dataType: 'json',
        complete: function(){
            return false;
        },
        success: function(result) {
            if(typeof result =='object') {
                $('#modal-spinner-seo-update').hide('slow');
                jQuery.each(result, function(field, message) {
                    $('#seo-'+field).next('div.error-message').html(message).fadeIn('fast');
                });
            } else {
                $('#modal-spinner-seo-update').hide('slow', function() {
                    $("#seo-widget-message-success").fadeIn('slow').delay(2000).fadeOut('slow');
                });
            }
            return false;
        }
    });

into a simple JavaScript xmlHttpRequest as following

    xhr = new XMLHttpRequest();
    xhr.onreadystatechange=function()
    {
        if (xhr.readyState==4 && xhr.status==200)
        {
            console.log(xhr.responseText);
            if(typeof xhr.responseText =='object') {
                $('#modal-spinner-seo-update').hide('slow');
                jQuery.each(result, function(field, message) {
                    $('#seo-'+field).next('div.error-message').html(message).fadeIn('fast');
                });
            } else {
                $('#modal-spinner-seo-update').hide('slow', function() {
                    $("#seo-widget-message-success").fadeIn('slow').delay(2000).fadeOut('slow');
                });
            }
            return false;
        }
    };
    xhr.open('GET','/metas/saveMetas?model='+model+'&f_key='+f_key+'&pagetitle='+pagetitle+'&keywords='+keywords+'&description='+description+'&niceurl='+niceurl, true );
    xhr.send();

and now everything seems to work fine. But I still do not understand why. Can anyone explain what I did wrong?