Nowadays many sites uses embedded map from Google for purposes like showing object location, drive-in way or more complex stuff. Recent Google Maps Version3 (V3) API becomes very powerful, but remained very clear and easy to use.
While developing site for real estate company I faced with necessity to display fancy, complex overlays on top of the map when user clicks on the marker.
There are some standard ways of showing so called info-windows. The problem is that it is not possible put complex formatting there or catch mouse clicks events.
To solve it I have to to dig into API internals and recent version V3 has some surprises here.