While masks sort of work for Internet Explorer 6-8, if you really want to create areas within areas, you can use polygons to split a shape into two connecting parts and combine them as a group. This example is created by rendering the outer circle in two "c-shaped" halves and rendering the inner circle separately. The other "shapes" demo uses masks and much less markup to do the same thing, but more complex situations where the inner area is not a solid color might not work as well in IE.
