I think consistency within an application is far more important than consistency across applications. And even if it were true that users hated the lack of consistency, it would fall on deaf ears: the web page developers can only influence their own page. They can't make Google or Mozilla or Apple come up with an actually usable error model, or any kind of good UI in general, so the only chance they have is to create a good UI for their own page, and hide the horrible defaults that each browser is reinventing.