http://www.w3.org/TR/html401/struct/....html#h-13.6.1
shape = default|rect|circle|poly [CI]
This attribute specifies the shape of a region. Possible values:
* default: Specifies the entire region.
* rect: Define a rectangular region.
* circle: Define a circular region.
* poly: Define a polygonal region.
Geht natuerlich haendisch, mit einem Proggie wirds leichter.