How to Sign-In with Sharepoint from the Javascript?

I used the following code to access the sharepoint from javascript

var soapDataString = "<soap:Envelope xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema' xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'> \
                              <soap:Body> \
                                <Login xmlns='http://schemas.microsoft.com/sharepoint/soap/'> \
                                  <username>testUser</username> \
                                  <password>testPwd</password> \
                                </Login> \
                              </soap:Body> \
                          </soap:Envelope>"

        // Call web service
        $.ajax({
            url: "http://abc-xyz-sp06/YY-SHAREPOINT/_vti_bin/Authentication.asmx",
            type: "POST",
            dataType: "xml",
            data: soapDataString,
            success: resultsFeedback,
            contentType: "text/xml; charset=\"utf-8\""
        });

function resultsFeedback(xData, status) {
    alert(xData);
    alert(status);
}

I followed from this article. I even put the above code in the ready function. But the function not entering into resultsFeedback and nothing happens. I am not able to sign-in from the javascript.