Ottengo questo errore:

This page is not Valid XHTML 1.1!
Below are the results of checking this document for XML well-formedness and validity.

Error Line 1 column 0: character "ï" not allowed in prolog.
ü/strong>?»¿<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xh


E' strano dato che la mia pagina inizia con

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html>
...


Grazie a tutti per l'aiuto