It works in all the major browsers - Mozilla Firefox 1.5+, Opera 9+, Safari and IE6+. On older browsers, it can use "jsgraphics" from Walter Zorn (if installed), else it'll degrade and your visitors won't notice a thing. CVI-lab: Get a fast impression of the effects and their illustration qualities.
You are able to create an image map, and then define the colors through the simple CSS class microformat:
<img class="mapper iborder00aa00 icolor00ff00" src="images/eu.gif" usemap="#map_of_europe" / />