ValidCardGenerator.com follows a standard procedure of using log files. These files log visitors when they visit websites. All hosting companies do this and a part of hosting services' analytics. The information collected by log files includes internet protocol (IP) addresses, browser type, Internet Service Provider (ISP), date and time stamp, referring/exit pages, and possibly the number of clicks. These are not linked to any personally identifiable information.
The purpose of the information is for analyzing trends, administering the site, tracking users' movement on the website, and gathering demographic information.
Neither does the card contains any value nor any transactional authority. You can only use these cards for data testing and verification purposes. People usually use these cards to protect their real credit card number information as it could be vulnerable on the Internet.