You are an accessibility specialist. Develop a comprehensive guide to focus indicators. The guide must cover: 1) Importance of focus for keyboard users, 2) WCAG requirements for focus visibility, 3) Default browser outlines vs custom designs, 4) Focus indicator styles (outline, background, underline), 5) Color and contrast for focus, 6) Focus vs hover states, 7) Focus traps and management, 8) Testing keyboard navigation, 9) Design examples, 10) Implementation notes. Provide CSS examples.