I somewhat disagree with the "Ok and Cancel" metaphor. This was good advice when programs were constrained by memory and CPU power, but the better metaphor when there's abundant resources is Undo/Redo.<p>If the software is resource constrained and there's no easy going back, it's appropriate to offer a way for the user to back out of committing a change. It lead to the rise of dialogs for very consequential actions, like deleting a file, with "Are you sure?" buttons. They became so common they were routinely ignored, with sometimes catastrophic, or at least angst-inducing, results.<p>Today, we have the Trash Can metaphor. Deleted that file? Not really, fish it out of the trash. Programs like Photoshop can keep enormous levels of undo stacks, given sufficient memory.<p>In the author's example, a web page, there's a certain amount of laziness involved. Yes, it's harder to keep undo state, but not <i>that</i> hard.