Not all browsers support these so alternate links should be provided. There may be several maps and images located in one html document. Alternately you could store map definitions in a totally separate document by specifying a full url. Be sure to specify ALT text as option in the IMG tag for users without images or client-side imagemap capability. 1.AREA tag followed by 2. kind of shape followed by 3.
Shapes can be rectangles, circles, or polygons.
Rectangles are identified by coordinates of topleft and bottom right corners. Circles are identified by coordinates of center and length of radius. Polygons are identified by the coordinates of each vertex. Here is the relevant code that creates that image. Note that the status bar at bottom of browser window indicates the URL as the mouse moves over sections of the image.