Using the History Palette
If you’re familiar with Adobe’s other programs, you know that the History palette is like a super-undo, or a time machine. The History palette lists your recent actions, and each new action is added to the bottom of the list. By looking at the list, you can see exactly what you did—and exactly where you went wrong. Clicking an action negates all the subsequent actions listed below. You can even negate particular events in the list. When you resume editing, the undone actions are removed from the list, and history is rewritten.
To use the History palette:
In a grouped palette, click the History tab to make the History palette visible. The palette lists the most recent actions, with the latest action at the bottom ...