You are not using Chrome or have not installed the application for this page.
If you haven't already installed this app, install it, close this page, and launch the app from the New Tab page.
Click Close background window.
Nothing visible should happen, but if the background window was open, it's now closed.
Note: If you briefly see a popup window, then the app is not installed correctly. Go back to step 1.
Click Open background window.
You should see a notification that the background window has opened. (It might take a few seconds to appear.)
Note: If you see a popup window instead of (or in addition to) a notification, then the app is not installed correctly; go back to step 1.
Click Open background window again.
Nothing visible should happen because the background window is already open.
Quit Chrome by clicking the wrench icon and choosing Exit.
On Mac, you can go to the menu bar at the top of the screen,
and choose Chrome > Quit Google Chrome.
Quitting Chrome closes all of its visible and background windows and all apps, including apps that use the background feature.
Either restart Chrome or log out and log back in.
You should see a notification that the background window has opened.
The generic source code for this app is available for download. The README tells you how to modify the code. See the apps documentation for more information.