The Administration interface checks input fields to prevent incorrect data to be entered.
That is why the Administration interface doesn’t allow you to switch to another page, configuration element, user or group, until you enter proper data in the page, configuration element, user or group that you are currently editing. If you are not sure how to edit a parameter, or you don’t know how to fill in a field, click on the Cancel button to leave the settings dialog without saving. You can reopen the settings dialog using the Server › Configuration menu item.