You won't be able to dismiss this by usual means (escape or click button), but you can close it programatically based on user choices or actions.
"These enclosure cards were perfect to go along with our formal invitations. We were able to work in information about the reception location, directions, and RSVP instructions (since we were having our guests RSVP online). Great back and forth with the custom designer. Only docked 1 star for design because I would have loved if it automatically came with the same back design as the invitation (instead of plain white)."
"I used this card for directions. It looked beautiful. I was very happy with the overall look. The quality was great. I do recommend."