So I’m up here in Maine, looking at my website, and noticing the blue top “David Seah” banner was missing. Not only on Firefox, but also on Internet Explorer! After some poking around, it turns out that Norton Internet Security has an advertising blocker in it that does not display any image named “banner.gif”. So for months, anyone who has been running Norton Internet Security has not see the top banner. I renamed banner.gif to topbanner.gif, and the problem has gone away. I suspect other ad blocking software does something similar.