Well, if OUT parameter is NOT supose to appear in any WebService, then
Visual Studio should have generated a compile time error right :)

Besides, I look at the Input and Output XML string, it is 100%
possible if I invoke this WebService (with *OUT* parameter) using HTTP
SOAP or from anyother client like Java.

The problem now is, I need to invoke using Ajax, and passing in the
Query string as the Cmd :(

POST /WebConfig/Utils/External.asmx HTTP/1.1
Host: 127.0.0.1
Content-Type: text/xml; charset=utf-8
Content-Length: length
SOAPAction: "http://tempuri.org/Test"

<?xml version="1.0" encoding="utf-8"?>
<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>
   <Test xmlns="http://tempuri.org/">
     <Msg>string</Msg>
   </Test>
 </soap:Body>
</soap:Envelope>

HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
Content-Length: length

<?xml version="1.0" encoding="utf-8"?>
<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>
   <TestResponse xmlns="http://tempuri.org/">
     <Name>string</Name>
     <Id>string</Id>
     <Res>string</Res>
   </TestResponse>
 </soap:Body>
</soap:Envelope>