Make the Affordance of Objects Obvious

The "affordance" of an element of interactive text is merely that which it is permitted to "do," functionally, by the interface that contains it. For example, text regions usually "do" nothing other than convey their informational content. If text is, indeed, interactive, then this affordance needs to be indicated by familiar devices such as color changes or underlining in boldface. Icons often permit linking to other information by clicking on them, and this affordance is usually indicated by graphically raising the icon to look like a push-button. Sliders and controls, especially, need to have their affordance made explicit.