What’s that URL for at the bottom of the Edit Calendar window?
This URL points to a read-only version of your calendar. You can only view it, not add, modify, or delete anything from it. The purpose of this link is to allow you to send it (copy and paste it into an email) to a person outside the calendar system, so they can look at your calendar. Notice that most functionality is missing, such as the New Event and New Task icons, Calendars, Groups and Options tabs, and so forth.