How to Undo Mistakes
Like a lot of programs, both the Editor and the Organizer remember the changes you make to an image or the catalog and enable you to undo those changes as needed. When you click the Undo button on the Shortcuts bar or select Edit, Undo XXX from the menu (where XXX is the name of the action you want to undo), Photoshop Elements resets the image or the catalog to the state it was before you made the most recent change. To undo the next most previous change, click Undo or choose Edit, Undo again.
Whatever can be undone can also be redone. Every time you undo an operationthereby going back one stepthat operation is remembered in a separate redo sequence for the image or catalog. If, after you click Undo, you click the Redo button or select Edit, Redo, the active image or catalog is re-reset to the stage it was in before the Undo command.
If you want to undo multiple changes, rather than clicking the Undo button repeatedly, use the Undo History palette in the Editor. Select Window, Undo History from the menu to display a listing of all the image changes you can undo. Changes are listed in the order in which they occurred, with the most current change appearing at the bottom. Drag the slider up from the bottom to undo changes, or simply select any change from the list. All the changes made up to that point will be undone in one step (changes that have been undone appear faded to indicate that they no longer apply to the current image). You can still redo the changes by dragging the slider back down or clicking a change that's lower in the list than the last retained change. To clear the history list of all changes for the current image, click the More button and select Clear Undo History from the More menu.
The Undo History palette makes it possible for you to undo multiple changes in one step.