I'm looking for for a simple tooltip that does two things:

(1) Hover or click a link or image to show a simple message. E.g. to display further information.

(2) Click a link to show a slightly bigger tooltip that can have HTML in it. E.g. click a link to open a form with a simple text box so the user can submit a message.

I want to do as much as possible with CSS and without JavaScript. Is this possible at all? What parts of the above can I do with pure CSS?