I see how to select font style, but I cannot find the settings for increasing the font size. In the album the image captions are appearing as rather small, and I would like to increase the font size a bit. Can you help me how to achieve that?

Thanks for the instant reply. Yes that helps. It is now how I would like it.

So: "lightbox-caption" controls the image captions.
I presume other codes control the display of other texts, like e.g., the text of miniatures.
Is there a list of such CSS-codes, so that I can adjust the sizes of other texts as well?

Indeed, there are no lists of the CSS selectors. Laza's skins, in particular, often have fairly dense CSS, so it can be a bit of a challenge to hunt things down. It's usually a matter of right-clicking on something, choosing Inspect, and then "feeling" your way around. Experimentation is usually called for.

In my own skins, I try to keep the CSS dead simple. Guess what .ja-slidetitle controls. Or .ja-slidecaption.