'Very pleased with how easy the website let me order, delivered, and notified when delivered. Outstanding job!'
'Couldn't be happier!'
'The flowers were beautiful, and delivered in a timely manner. Thank you so much for making this transaction go smoothly. I would definitely use this flower shop again.'
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.