Thanks for your answer,
but in this case, how can I do this ? Because, if I want to allow anonymous, as I'm using NTFS mode, I'm supposed to add the "Anonymous user" in the security settings of the qvw file, but ... it doesn't exists??
(with IIS, It exists a IQVS user which represent such an "Anonymous user" but, here, I'm using the QlikView Web Server).