Mountain Lion offers a new feature called Power Nap, but since it’s limited to only a few recent laptop Mac models, most people probably haven’t seen it. In short, Power Nap enables supported Macs to wake up briefly to back up via Time Machine, check for email via Mail, receive new messages in Messages, and update iCloud-related data, including calendar events, contacts, reminders, notes, iCloud documents, and photos in Photo Stream. Over at Macworld, our friend Dan Frakes explains just what Power Nap can do, how you use it, why it works on so few models, and more. follow link
Go Back and Forth Fast in Preview
If you're reading a PDF in Apple's Preview software, and you follow a bookmark or an internal link to move around within the PDF, you can quickly return to where you were by pressing the keyboard shortcut Command-[ (that's Command-Left Bracket). Or, you can choose Go > Back.
The command works iteratively, so you can go back to just the previously viewed page or if you issue the command again, to the page before that, and so on. There's also an equivalent Go > Forward (Command-]).
Dan Frakes Explains Power Nap