Can it be any visitors? Or registered users of my site?
Any visitors, not necessarily registered.
Below it says "If you use .html files as the website pages, the visitors on the site are not taken into account. Users must use at least 1 content module (Blog, Site News, Catalogs, Forum, Guestbook etc.)."
If your website consists only of static .html pages, no visitors are counted. What's the address of your website?
And buying a domain name does not affect the website being deactivated. If you want your website to never be deactivated for inactivity (no matter whether it has visitors or not), you need to become a premium user - buy any of paid packages for any period.
I'm not active on the forum anymore. Please contact other forum staff.