Recommended for iMac models released in late September 2013 (see “Apple Updates iMac with Faster CPUs and 802.11ac Wi-Fi,” 24 September 2013), Apple has issued iMac 10.8.5 Supplemental Update 1.0 for those models with an Nvidia GeForce GT 750M graphics processor running OS X 10.8.5 Mountain Lion. The update fixes two bugs: one that caused external drives to eject after the iMac goes to sleep and another that prevented certain USB Bluetooth adapters from working. (Free update, 17.1 MB)
Sleep (and Lock) Your Screen
When you are walking away from your computer, it's fairly common practice to start your screen saver and lock your screen. But did you know that there is a built-in keyboard shortcut in Mac OS X to sleep the screen?
Press Control-Shift-Eject and your monitor sleeps without engaging the screen saver.