Haber si alguién me ayuda porque cuando válido doctype me dice que:
Result:Tentatively passed validation, 1 warning(s)
DOCTYPE Override in effect!
The detected DOCTYPE Declaration "<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">" has been suppressed and the DOCTYPE for "XHTML 1.0 Strict" inserted instead, but even if no errors are shown below the document will not be Valid until you update it to reflect this new DOCTYPE.
Y mi doctype es:
<!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="es" xml:lang="es">
Vamos yo lo veo correcto.