You can undo your last action using the Undo command found in the Edit menu.
If you would like to undo more than one action, you may use the Step Backward command or the History palette. You can undo your most recent action using the Undo command found in the Edit menu. If you have mistakenly deleted an element or added an unwanted element to an image, you can use one of Photoshop's undo features to correct the mistake. This article is based on legacy software. (Archives) Adobe Photoshop CS3: Undoing Previous Actions
