Why does Word think there's Italian in a document that shouldn't contain any?

Some text in the document was marked as Italian, perhaps while pasting text from the Web.

Do not choose the "Never show again" option. To undo :

1. Use Ctrl+A to select the entire document
2. Click on the Language panel at the bottom-left border
   Or alternatively, in the Review tab, Language group, click Language, and then click Set Proofing Language.
3. In the Language dialog that opens choose your language
4. Click OK and the document should now be entirely of that language

If the problem still exists, in the Review tab, Changes group, choose Accept -> Accept All Changes and Stop Tracking, then repeat the above.