<style type="text/css">.thumbnail{position: relative;z-index: 0;}.thumbnail:hover{background-color: transparent;}.thumbnail span{ position: absolute;background-color: ffcc00;padding: 5px;left: -1000px;border-right: 1px solid ff3300;border-bottom: 1px solid ff3300;border-left: 1px solid ffff00;border-top: 1px solid ffff00;visibility: hidden;color: black;text-decoration: none;font-family:arial;font-size:11px;}.thumbnail span img{ border-width: 0;padding: 2px;}.thumbnail:hover span{ visibility: visible;top: 20;left: 60px; }</style> Click here to view a bigger version of my map!
You can also make your own, it's free!