JS runtime error: Object expected : in Binding

Hi,

I have retrieve data from database using json. But i got an error like JS runtime error: Object expected

In aspx

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js"></script><script type="text/javascript">$(document).ready(function () {$.ajax({
            type: "POST",
            contentType: "application/json; charset=utf-8",
            url: "WebForm1.aspx/DisplayData",
            data: "{}",
            dataType: "json",
            success: function (data) {$("#lbltxt").text(data.d);
            },
            error: function (result) {
                alert("Error");
            }
        });
    });</script>

<label id="lbltxt" runat="server"></label>

In aspx.cs

[System.Web.Services.WebMethod]
        public static string DisplayData()
        {
            return DateTime.Now.ToString();
        }