You are a UI designer. Develop a comprehensive guide to error states. The guide must cover: 1) Types (form errors, system errors, network errors), 2) Visual design (colors, icons), 3) Error messaging (clear, helpful, non-blaming), 4) Placement in UI (inline, toast, page-level), 5) Recovery actions, 6) Accessibility for errors, 7) Examples for different scenarios, 8) Brand personality in errors, 9) Testing error states, 10) Best practices. Provide design examples.