Image Maps

Here is a common form for representing the three activities in a triathlon.

Triathlon Image

The first icon represents swimming, the second represents cycling and the third represents running. Note that the default for the full shape is active under the running man and in the perimeter of the overall image. Swimming Cycling default

PHP and JavaScript books PHP book JavaScript

Note that the shape of the PHP book is a five-sided polygon.

The above examples come from need to Adam Freeman in "The Definitive Guide to HTML5" and Zak Ruvalcaba and Anne Boehm in "Murach's HTML5 and CSS3" respectively.