In the Calendar web view, there are three panes (or columns): The list of Calendars, the list of Events/Tasks, and the "Planner" view. The list of Calendars on the left can be hidden, but the other elements are fixed - they can neither be hidden nor resized. This is quite annoying, especially for people who are subscribed to multiple calendars (of other people) and just want to have an overview of the planner.