Aha!
But strangely, that extra ; is NOT what I have put in the Neptune Code UI.
It seems to be getting mangled, but not until AFTER the jAlbum preview (when everything is as intended).

This would require magic. There is nothing in the preview or uploading processes that could possibly alter the contents of common.css.

Please attach the jalbum-settings.jap file that you're using. Either something is wrong in there, or it's not getting uploaded properly, or there's something being cached in the browser.

“Any sufficiently advanced technology is indistinguishable from magic.” A.C. Clarke

Here is the file.

But you should not be working on my mysterious problems at Chrismas time

Magical Mystery solved

Apparently I made a "temporary" change to the jAlbum "Output directory" to allow comparison of "Xmas2023" with "Xmas2023TEST" and forgot to change it back and remake before uploading it.

There are still a few minor changes required but those can wait until I get back.

Thanks muchly for your invaluable help, and have a great Christmas.

You can't rely on what the browser's developer's tool bar shows you. That just reflects the browser's desperate effort to make sense of incorrect syntax. You need to look at the actual common.css file on the server.

You should explore the newest option in virtually all of my skins: uncropped theme image. It would achieve what you're after, without any custom CSS, and its attendant problems.