What you need to know
A page is not complete when only its success state is polished. People need feedback while content loads, a recovery path when it fails, and a clear explanation when there is nothing to show.
How to apply it
Model request status explicitly, show skeletons or progress only when useful, include a retry action for recoverable errors, and make empty states explain what the user can do next.
Common mistake to avoid
Do not display an empty white panel for errors or empty results. Avoid infinite spinners that never tell users whether the request failed.