CSS for Responsive Websites
CSS controls the visual presentation of a web page: color, typography, spacing, sizing, layout and responsive behaviour. HTML provides the document structure; CSS turns that structure into a consistent interface.
How the cascade works
Styles can target individual components or a shared design system. The cascade, specificity and inheritance decide which rule wins. Clear naming and predictable layers reduce conflicts and make the codebase easier to maintain.
The term CSS3 is still common, but modern CSS evolves through separate modules. Check support for the specific feature you plan to use instead of relying on a version number.
Responsive layouts
Responsive pages adapt to available space, input method and user preferences. Use flexible sizing, media or container queries, Flexbox and Grid. Choose breakpoints when the content needs them—not from a fixed list of device names.
Flexbox
Flexbox is ideal for one-dimensional components such as navigation, toolbars, button groups and aligned rows or columns.
Grid
CSS Grid coordinates rows and columns, making it effective for page regions, galleries, card collections and complex layouts. See the CSS Grid and Flexbox comparison for a practical decision guide.
Accessibility and performance
Motion should clarify interface changes without distracting readers. Respect prefers-reduced-motion, preserve visible keyboard focus and maintain sufficient contrast.
Fonts, critical styles and large background images affect rendering speed. Test layout stability, overflow, zoom and real mobile screens before release.
Testing and related guides
Verify important templates, forms and navigation in the browsers your audience uses. JavaScript should enhance a usable layout rather than repair an unclear structure.
Practical CSS guidance
