What is it? The “Save” button, of course.

This button should not exist at all — any program should save my data by default, and the only button should be “Revert”. It’s because I want to save what I typed in 99,9% of cases, and I don’t want to save in only 0,1%. UIs have the wrong default. Save button is the programmers’ invention — they’re lazy, and not saving things is much easier to code than saving. People accepted this in the 1980s, but today is 2014, and we shouldn’t accept anymore.