Hover over either of the irregular shaped countries America or Africa (or the Links below) and a message box will pop up and the country and links will be highlighted. The "active area" will hug the shape of the country very closely.
The "shape" attributes and "coords" attributes have been added to the anchor (which is allowed by the specs) and defines the target area. For browsers that don't recognise the "shape" and coords" attributes then "area "elements have been added and duplicated duplicated with the required information (also valid) to allow a fallback mechanism but of course the highlight will be missing for the country.