I have a single jpeg image that contains four graphic gray stars. I want the effect where if you scroll over the a star the image changes to a yellow star. Just like the rating tools you see on netflix and amazon. Does anyone know if its possible to create the hover effect (and change the image) for specific coordinates on a single image?

I don' think you can do a hover with a map. Maybe try slicing the image and then do a table with cellspacing="0" and do the manual <A onmouseover> or a:hover hover method.