Two things every program should have - Instant on/instant off automatic load/save and unlimited undo/history.
A useful feature for complex sites would be the ability to click to view the path you took through a web site (history) and recreate it the next time you're there (Journal).
Solution: Archy never loses your work. This shouldn't be a groundbreaking innovation in computer design, but it is. You never have to save because it's done for you automatically. Your data is stored in such a way that if your computer crashes, your information will still be there the next time you start Archy up.
You don't have to worry if you make a mistake. The UNDO command can reverse your steps all the way back to the first thing you ever did on Archy. Quitting Archy has no effect on UNDO's elephantine memory.
Source: Core Principles - Raskin Center