// Hiding the "Add to Calendar" checkbox
#settings span[class$="gridCol"]:nth-of-type(2) span[class$="gridCol"]:nth-of-type(4) {
    display: none;
}

// Hiding the "Conference" block in the calendar
#edit_calendar_event_form_holder span[class$="gridRow"] span[class$="gridCol"]:nth-of-type(6) {
    display: none;
}