Why does this icon flash in my address bar?
When opening Safari, whether I just closed the window or quit the app, this icon may pop-up in the address bar. Now the top half is the icon of a dutch public transport company, however the red dots are completely unfamiliar. Strangest thing, this icon shows up for less then a second and only when I start safari or open a new window. The correct icon, in this particular case Facebook, is shown directly after.
Now, what can this icon possibly be? Hopefully it doesn't mean that I'm compromised or that I'm being tracked whatsover. Can you help me out?
MacBook Air, Mac OS X (10.7.2), Late 2010