Thank you for that tip. Anyway, we will not list that page since on their page http://www.flashcardexchange.com/leitner.php they have published <b>copyrighted material</b> taken from <a rel=nofollow target=_blank href=http://learn.how.to>http://learn.how.to</a> <b>without permission</b>.
Further, let us note that said site is not entirely free. Certain features (such as exporting downloaded flashcards to a different file format) are available only to users that have paid a fee.
Finally and most interestingly, we could find no corporate information on that site other than a P. O. Box. Considering they ask their visitors to enter their credit card information, we regard that website as non-safe.
Thank you for all your suggestions and have a good day.