The appearance of a page or component when no content is available, such as an empty search results or new user dashboard. Well-designed empty states guide users toward actions that populate the interface. Include helpful messaging and clear calls to action rather than leaving users stranded.

The visual appearance of an interactive element when it receives keyboard focus, which is critical for accessibility. Focus states must remain clearly visible; do not remove them without providing an equally visible replacement. A strong focus style improves usability for keyboard and assistive-technology users.

The current condition of a component or interface element, such as default, hover, active, loading, or error. Managing state effectively enables responsive, interactive experiences. Design all relevant states and transitions between them.