When I press Option+D key in OS X, the current application loses focus. And if I press it again, the current window gets focus back.
How do I know which application bind that or how to avoid it. I checked the shortcuts in System Preferences and there isn't anything like Option+D keybinding.
System version:
ProductName: Mac OS X
ProductVersion: 10.11.4
BuildVersion: 15E65
This annoys me so much.