There's nothing wrong with the demo itself, but with the demoed ads -> They should appear and disappear according to the movement of the mouse pointer on "whitespace" right?

For me, that's what isn't working... the ad starts as visible, flickers on the mouse of whitespace, and stays visible after I move the cursor back into the demo. I see the default add as aligned top-left from the corner of the browser window: is that correct? (it covers your logo/title bar)