ajax无刷新post提交总大小问题

var xmlhttp = leleAJAX();
    xmlhttp.open("post",url,true);  //使用post方式提交。。
    xmlhttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
    xmlhttp.onreadystatechange = function()
    {
        if(xmlhttp.readyState==4)
        {
            if(xmlhttp.status==200)
            {
                var info = xmlhttp.responseText;
                if(info=="验证码输入有误"||info.indexOf("失败",0)>0)
                {
                    $("leleMessage").innerHTML = marquee1 + info + marquee2;
                    return false;
                }

                $("leleMessage").style.display = "none";
                msgbox(alertWidth,info);
                $('reset').click(); //触发点击重置按钮
                delEditorContent();//清空编辑器内容
            }
        }
    }
    xmlhttp.send(url);
    return false;