Guidelines for Using XML-Based Output Templates with HTTP Clients
If you want to use an XML-based output template to return output to an HTTP client, keep the following points in mind:
Make sure the output template generates a valid and well-formed XML document.
Make sure the template contains a <meta> tag that sets the Content Type to “text/xml”.
If your client is a browser, make sure it can accept and display XML (for example, Microsoft Internet Explorer 5.0 can display XML) or that the client machine has a MIME definition for Content-Type “text/xml”.