Zenphoto version 1.3.1.2 [5831] (Official Build)
Current gallery theme: zpGalleriffic
PHP version: 5.2.17

Hello. When I mark an album as unpublished, or when I delete an album, the change is immediate in the back end. However, if I logout, it still shows up on the front end, even though I refresh my browser or after I quit and restart my computer. Any idea? Thank you.

You possibly have the static_html_cache plugin enabled so you still see the outdated cached page. Clear the cache via the button on the overview page.

Otherwise your browser cache is playing tricks on your or the server does some over persistent caching itself.