YOu need java for it to be correct in IE but you can use CSS with incorporated java.
Not true, with a little tweaking (read: exploiting inaccuracies in IE's use of CSS) there is no reason (that I'm aware of) why pure CSS cannot be used here. As seen.to recommended, the sliding doors technique would be a good one to use. Just combine both images into one. An added advantage is that it keeps things tidier for when you want to update the image.
Note: It was done very quickly, and I've made no effort to check of browser bugs, inconsistencies, etc. It's 3am so please forgive any and all mistakes.