For the last few days the Amazon UK home page has had the following graphic:
The idea here is clearly to convey that there is something important going on here, something that you, the customer, should take a minute or two of your day to attend to.
But, to me, it doesn’t work. It comes across as an exception to the normal reading of the page—which was the intention—but, not in a good way. It is overserious. The “Dear Customer” is rather jarring, and makes you expect something like “In recent days you will have read stories concerning amazon.co.uk in the press; we would like to refute these allegations in the strongest terms…” or something else rather negative.
The general lesson here is, I suppose, that you have to be very careful when leaping out of the regular visual language of web pages. It is very easy to get the reader to attend to something presented in a different visual language—but then, you need to ensure that they are getting the right implication from it.