Your XHTML document must start with an XML declaration. You must use XML version 1.0. You must use XML encoding="UTF-8" explicitly. The standalone pseudo attribute must not be used. The XML declaration must not contain insignificant whitespace. The DOCTYPE declaration is missing. There must be no comments or PIs between XML declaration and DTD. There must be exactly one newline between XML declaration and the DTD. The DTD must be for XHTML 1.0 Strict!.