Html Tailwind Guideline: Z-Index — Use Tailwind z-* scale. Description: Consistent stacking context with predefined scale. Do: z-0 z-10 z-20 z-30 z-40 z-50. Don't: Arbitrary z-index values. Good Example: z-50 for modals. Bad Example: z-[9999]. Severity: Medium. Docs: https://tailwindcss.com/docs/z-index.