Quite right -- thanks for catching that. The namespace URI I used in the column *was* at one time the correct one for Transitional XHTML (see, e.g., http://www.w3.org/TR/1999/xhtml-modularization-19990406/DTD/doc/xhtml1-t.html). But that is no longer the case. The correct URI is indeed http://www.w3.org/1999/xhtml.