Hi Xmlizer, I believe that the official reference to XHTML is to a DTD such as: <?xml version="1.0" encoding="iso-8859-1" ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"> ... </html> You should be able to use this format. John -----Original Message----- From: oxygen-user-bounces@oxygenxml.com [mailto:oxygen-user-bounces@oxygenxml.com] On Behalf Of mozer Sent: Thursday, 3 July 2008 2:40 AM To: Oxygen User Subject: [oXygen-user] html does not allow namespace declaration on the rootelement Dear, with the following file <?xml version="1.0" encoding="UTF-8"?> <html xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.w3.org/1999/xhtml"></html> I have the following error E [Xerces] Attribute "xmlns:xsd" must be declared for element type "html". Can you explain me how to workaround this ? Regards, Xmlizer