So, Apple likes to change things; this much is a given. The software developers behind the operating system, OS X, are no different. They’re constantly changing the way things work from iteration to iteration of Apple’s computer software.
In Snow Leopard, when you made changes to a document and tried to close that document, you’d be asked by your Mac, in essence, “are you sure you want to do that?” and you could tell it to save the changes you made, or discard them. It was a way to let us know that there had, in fact, been changes to the document, whether we meant them or not.
In Lion, that little “feature” went away. Documents in Lion were always saved, regardless. This is a neat feature, in some ways, but it keeps you from knowing if you’ve made any unintended changes.
Luckily, Mountain Lion lets you choose the way you want it to work. If you want to have that failsafe “are you sure” save changes dialog, you can enable it. If you don’t want it, you can disable it.
Open System Preferences from your Dock, or the Applications folder, or the Apple menu (if you’ve read these tips for a while, you know the drill). Click on the General icon in the upper left corner of System Preferences to open the General preferences pane. In the third section from the top, you’ll see the item, “Ask to keep changes when closing documents.”
Click on that to revert your Mac to the Snow Leopard way of doing things. When you close a document with any unsaved changes, you’ll get a dialog box which will let you decide what to do with the changes. If you leave that box unchecked, your Mac will just save everything you do, and won’t ever let you know that it’s done so, which is a faster and perhaps safer way to keep your documents up to date, but it could lead to some unintended changes creeping in.
Whichever way you choose, we still like you. Especially if you choose to check the box.