VoiceOver for Mac OS X is a very helpful assistive technology for blind Mac users – unlike screen readers for Windows, which cost hundreds of dollars, it’s built right into OS X. Unfortunately for sighted users, occasionally people turn in on without meaning to and the results can be confusing …

If your Mac won’t stop talking – reading what’s on-screen in a computer-generated voice – and you see a thick black line around everything and possibly also the black box or caption bar at the bottom of the screen like this
 

The good news is that turning VoiceOver on and off is generally really easy – just hold down the command key (⌘) and tap the F5 key.

It’s possible to disable this command-F5 shortcut, so if it doesn’t work you’ll need to follow these steps:

1. Choose “System Preferences” from the Apple () menu.
2. Click on the “Accessibility” icon in System Preferences, then the “VoiceOver” item in the list on the left.
3. Uncheck the “Enable VoiceOver” box.