HTML/CSS: How does Google create this drop shadow over their maps?

Question

Question: How does Google create the dropshadow next to the vertical scrollbar over the Google Map?

This is a screenshot depicting exactly what I'm talking about.

This seems to be regardless of browser (IE, Firefox, Chrome) and platform (Windows, Mac, Linux).

Answer 1

It's actually a series of five razor-thin DIVs, each with decreasing opacity, stacked next to each other. You can see this for yourself by using Firebug and clicking on the shadow area.

Answer 2

IE 8: Use F12, select the arrow control, then click on the element you're interested in.

In this case, it's 5 divs overlapping, widths 1-5px, all with a style of "filter: alpha(opacity=x); opacity:0.x;", x going from 10 to 02