OS X’s Help menu is fantastic, if underrated. It even lets you find menu commands by highlighting them when you search within the Help search field. If you hit enter after typing in a search term, however, you’ll get the Help Viewer, a useful little hyperlinked app windwo that just, well, hovers over all your other app windows. This is good to start, but when you want to hope back into the app you’re trying to learn more about, the Help Viewer stays on top, even when it’s not the mouse focus.
Want to fix that? Here’s how.
Launch Terminal app, which is in the Utilities folder, which is itself inside the Applications folder. Once the app launches, type or paste the following command in:
defaults write com.apple.helpviewer DevMode -bool true
Hit enter on your keyboard, and you won’t see any visual acknowldegement of what you just did – no admin credentials or anything like that. You can check to make sure it worked by launching the Help Viewer, and then bring a different app to the front.
If you want to reverse this feature, simply type or paste the following into the Terminal app:
defaults write com.apple.helpviewer DevMode -bool false
This should work in most modern versions of OS X, including Mountain Lion, Lion, Snow Leopard, and earlier.
Source: OSX Daily.