Undo View Change cancels the last change made to the current viewport. Redo View Change cancels the last Undo in the current viewport.
These commands act like Undo and Redo on the main toolbar and Edit menu, but operate on a different list of events. They affect changes made to the viewport, rather than changes made to objects in the viewport.
Use Undo View Change and Redo View Change when you have inadvertently made a view unusable by zooming in too close, or rotating the wrong way. You can keep stepping back until a useful view appears. The keyboard shortcuts are handy for multiple commands.
You can also access Undo View Change by right-clicking the Point-Of-View viewport label and choosing Undo View Change from the POV viewport label menu. This menu choice shows the last change you made in that viewport: for example, “Undo View Zoom.” Each viewport has its own independent undo/redo stack.
Camera and Spotlight viewports use object-based Undo and Redo, because the viewport change is actually a change to the camera
or spotlight object. In these viewports, use Edit 
Undo (Ctrl+Z) or Edit Redo ( Ctrl+Y ).
Cancels viewport changes. The name of the change you're undoing is displayed in the View menu beside the command.
Undo is useful when you are working with a background image in the viewport. You can zoom into the geometry to adjust it, then use Undo Viewport Zoom to restore the original alignment of the geometry with the background.
