You can have an unlimited number of visitors to your calendar.  A visitor is anyone who can access public calendar categories over the internet and cannot login to view private categories.  Registered users are entered by you into the calendar database and are able to login to view private categories.  The number of Registed Users allowed for each subscription plan is:

1. Basic Subscription: 25 Registered Users
2. Standard Subscription: 50 Registered Users
3. Professional Subscription: 100 Registered Users

Registered Users can also be designated as category Managers and Administrators.