Validation document xml Encodage

Bonjour à tous. lorsque j'essaie de valider mon documennt xml j'obtiens ce message:

Citation:

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Missing "charset" attribute for "text/xml" document.

The HTTP Content-Type header (text/xml) sent by your web browser (Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.5 (KHTML, like Gecko) Chrome/4.0.249.78 Safari/532.5) did not contain a "charset" parameter, but the Content-Type was one of the XML text/* sub-types.

The relevant specification (RFC 3023) specifies a strong default of "us-ascii" for such documents so we will use this value regardless of any encoding you may have indicated elsewhere.

If you would like to use a different encoding, you should arrange to have your browser send this new encoding information.

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Ainsi qu'un autre signalant un accent aigu. je sus débutante. Que faire? Merci.