- Event class: join_event has to return false when the join date is not within join start and end date.
- Event class: join_event has to return false when apply is 0.
- UI(Nav): Event is not easy to share
- UI(Nav): Album / Photo is not easy to share

IE bugs:
- Nav: window.event bug (<IE9)
- Add/Edit Event: if there's an error, the edit panel is in an incorrect position after clicked the back button