Hello Acrylian,
Thanks, works much better now

.
I only get this code when I'm on an album page with only album thumbs and no image thumbs:
`Warning: Invalid argument supplied for foreach() in /srv/jackdaw/www/www.spoenk.nl/beeldend/zp-core/zp-extensions/tags_from_album.php on line 122`
I placed the function at the bottom of album.php, so the function is called on pages with just albums and pages of image thumbs. I hope it has nothing to do with that normalizecolumns thing, because I don't use that.
Also I'd like to now if there is a function which can check if the images inside an album has any tags. That way I can hide the line 'Tags inside this album:' if there are no tags.