Show or Hide the History Palette
Menu: Window Showing/Hiding History
F9 shows or hides the Actions palette. Also use it to show or hide the History palette if you haven't changed the default grouping of the Actions and History palette. To show History if the Actions palette is not open , press F9, and then click the History tab. To hide both the History and the Actions palettes, press the F9 key until they both disappear.
Photoshop Histories allow for snapshots whereas ImageReady does not. The Photoshop History palette has icons to create a new state and to create a new document from the current state; you won't find either of these in ImageReady.
Menu: History Step Forward
Mac: Shift + Cmd + Z
Win: Shift + Ctrl + Z
Menu: History Step Backward
Mac: Cmd + Option + Z
Win: Ctrl + Alt + Z
Photoshop 6 and ImageReady 3 allow you to choose from three different Redo shortcuts via the General Preferences. You can switch the Redo keystroke to match ImageReady, match Microsoft style, or remain Photoshop style. Note: Picking anything other than Photoshop style loses the ability to undo and redo history. The default in Photoshop 6 is that (Cmd + Z) [Ctrl + Z] toggles between undo and redo of the last thing you did. The default in ImageReady for (Cmd + Z) [Ctrl + Z] is set to multiple undo.
Here is what happens when you change the preferences:
Duplicate the History State (Other Than Current)
Mac: Option + click the state
Win: Alt + click the state
Create a New Snapshot
Mouse: Click the New Snapshot icon
Create a New Document from the Target Snapshot
Mouse: Click the New Document from Current State icon