dedeCMS 织梦ajax跨域提交自定义表单和验证码问题

<script type="text/javascript" src="http://apps.bdimg.com/libs/jquery/1.6.4/jquery.min.js"></script>
<script>
function send() {
    $.ajax({
        cache: true,
        type: "POST",
        url: "http://B站域名/plus/diy.php",
        data: $('#diyform').serialize(),
        xhrFields: { withCredentials: true },
        crossDomain: true,
        success: function(data) {
            if (data == "success") {
                alert('发送成功!');
            } else {
                alert('发送失败!');
            }
        }
    });
}
</script>
<form action="" enctype="multipart/form-data" method="post" id="diyform">
    <input type="hidden" name="action" value="post" />
    <input type="hidden" name="diyid" value="2" />
    <input type="hidden" name="do" value="2" />
    <input type="hidden" name="dede_fields" value="name,text" />
    <input type="hidden" name="dede_fieldshash" value="c2be5bb5ec45d9d01ca9f60dc469b3fb" />
    <p>姓名：<input type='text' name='name' id='name' /></p>
    <p>验证码：<input type="text" name="validate"><img src="http://B站域名/include/vdimgck.php" align="absmiddle" onclick="this.src='http://B站域名/include/vdimgck.php?tag=' + Math.random();" style="cursor:pointer;"></p>
    <div onclick="send()">提交</div>
</form>