Some other things I’ve noticed.

- This is implicit in “lightboxes are not pages,” but I’ve been tempted to build flows with multiple lightboxes in sequence. I think this is almost always a bad idea.
- Mac people expect close buttons on the upper left. If most of your users are Mac people, you might do that.
- Transition animations–especially for opening a lightbox–can be a nice touch if done subtly.
- I’ve started seeing a lot of “semi-lightboxes” — really pop-ups with a semi-transparent frame. Facebook in particular does this.