The URL that it opens is http://helpx.adobe.com/photoshop/topics.html.
It seems to happen relatively often when the color picker is opened, particularly via the fx pane. It continually opens multiple pages until the color picker / fx pane / etc. is closed.
Also, this message appeared the last time this occurred:
Color Picker (Stop Color)
There was an error initializing the Adobe Help application. You may need to re-install the application and the Help component.