Hmm, I guess I haven't made myself very clear :)
These two images were one box I made in PS, then I cut it in two. They should match up perfectly. (NB the box has a slight gradient as noted by lucy24).
Here is an example page. This page is directly calling the two images from my earlier post.
On my Mac this looks fine in Firefox, Chrome and Opera, but in Safari the two parts of the box don't match. Can anyone explain why? Thanks!