It depends what detail level you want, really. Trying to do a highlighting effect when hovering over an area is going to need some serious image mappery. Either way, you are looking at a large number of images (or one huge image) to handle the highlighting of all the countries.
A more realistic approach would be just to go with continents or geographic regions, and then go into finer detail with a drill-down system.
Simon Jessey | Keystone Websites
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