Thank you for the reply.
However, this does not seem to work.
When I save the contents of the editor to the database the !Doctype tag remains in the editor HTML window.
But if I close the editor after saving and open it again - getting the saved html from the database - the !Doctype tag is no longer there.
If I look in the database after saving, I notice that the !Doctype tag has not been saved in the database.
As you will appreciate, this is a major problem in the creation of web pages using the editor.