Let’s say you have a map of the world and you want to be able to highlight the country (or state, or county, etc.) as the cursor hovers over it or it is tapped.
Doable!
First, the map should probably be vector. SVG is almost certainly the right image format choice here. It will give us a crisp looking map at likely a reasonable size, and most importantly, give us the interactivity and easy styling we need.
http://mediatemple.net/blog/tips/map-rollovers/
origin - http://www.pipiscrew.com/?p=6513 map-rollovers