>>I believe, it should be: "Are you sure, you want to delete these items?" Yes/No
>
>You don't need the comma after "sure", but otherwise, your version is correct English.

The better point here would be what to write on the buttons after such a question. "Yes/No" means "yes I'm sure" and "no I'm not sure" - so what,if the user is not sure, it would require further means of investigating the reasons why would he want to delete, or - ?

The other version "Please confirm..." also wouldn't go with "yes/no", IMO it'd rather go with "OK/Cancel", so the user either okays or cancels the deletion.

I've been bitten with not only ambiguous questions, but also with various choices of given answers, often enough to always think twice before writing a message and the buttons.

Once back in Hungary, when the big app was still in diapers, I used to have an error message which just notified the user something has happened (and did the logging in the background), and restarted the app. It had an OK button - "okay" is quite a common word around the word, widespread in Hungary as well... well not really. "Ok" in Hungarian means "reason why, cause of", so some of the doctors/users expected the full explanation of the event to pop up when they click OK.

It had to be rephrased as "O.K.".