This attribute should be used to set the usage for common buttons. Some platforms display these buttons with a small icon indicating their usage. This should be used in place of the image attribute. Possible values include: accept, cancel, help, open, save, find, clear, yes, no, apply, close, print, add, remove, refresh, go-forward, go-back, properties, select-font, select-color, network. If you are using a button that matches one of these common usages, use the icon attribute to indicate this. See the appearance of the different icons on some available platforms.