Image maps are a neat little HTML trick (that I really hope works in Blogger). They let you assign shapes on an image (circles, rectangles, and arbitrary polygons) with attributes. They can display text when you mouse over them, link to websites (useful for things like an interactive periodic table), or act as a detection (on click or mouseover) that triggers other events.
W3C specification document
I made one from this map I made of the Abraham Lincoln, a train in Illinois (now integrated into the Lincoln Service name). Mouseover tips show tips for making geographics maps of train systems; the title links to the article on Wikipedia.
RIP Chuck Berry
3 days ago