it worked with lightbox!
But I have one more question: is it possible to specify a size of the photos in the lightbox? You can show them fullscreen, but I would like to show the photos a bit smaller, is this possible?

www.mspc.be/mastercar/fotos.php

The lightbox shows the images in their original size/dimensions.
You can fiddle with the CSS and add something like:

.dmxLightboxImage img {
    max-width: 600px !important;
}

in your custom css file to override the default behavior.