'Thank you for your prompt delivery service. This is the first time I have ordered flowers this way and I was very satisfied. The ordering process was very easy and the flowers were very nice. Thanks again.'
'The flowers were beautiful, just like the picture. Thank you very much for being so prompt.'
'Thanks very much! Wonderful service! Confirmation greatly appreciated!'
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.