BTW, there I observed bug in the placement of the tumbnails - the third one (at least in the first row) is placed about 10 pixel or so lower than the two preceding ones. That does not look very pretty. I tested that in ice-treff.de and don't know which version of "my little forum" is running there.

Can you please provide an example here, in this forum?

OK, here in separate post. Buit it works OK here... I don't know what I made differently. I used only the preview and did not actually post the message, so I can't easily reproduce the problem, since I also do no longer remember which images in which resolution I had used.