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GMail shows a very useful UI elements which is the yellow status box that appears when an image is deleted, for example.
The features of that elements are that it shows a short text, it can have different styles, and present links for actions. The messages would disappear with time, but can be dismissed by the user with a small close button usually.
So this element is what says: "Item has been deleted" or "Dramatic server error" in the following mock.
Usually those items pile up and they may collapse when a message is repeated, with a counter, like it happens for chrome console messages.
These elements are really powerful for web applications for example, because they can inform the user about general communication with the server side, and they are very versatile.
What is the correct term to describe this UI element? I have heard it being called "butter box".