Best practices checklist

Responsive design checklist

✓ Viewport meta tag present. ✓ Mobile-first CSS approach. ✓ Flexible widths (%, em, rem). ✓ Media queries for key breakpoints. ✓ Images responsive (max-width: 100%). ✓ Touch-friendly buttons (44x44px). ✓ No fixed-width layouts. ✓ Test at 320px, 768px, 1024px, 1440px. ✓ Core Web Vitals optimized. ✓ WCAG 2.1 AA contrast ratio.

Common pitfalls to avoid

❌ Omitting viewport meta tag. ❌ Fixed widths and pixel-based layouts. ❌ Hover-only interactions. ❌ Text too small (< 14px on mobile). ❌ Small tap targets (< 44px). ❌ Unoptimized images (images larger than needed). ❌ Not testing on real devices. ❌ Assuming all screens are 16:9.

Minimal responsive CSS template

Start every project with these essentials.

* { margin: 0; padding: 0; box-sizing: border-box; }

html { font-size: 16px; }

body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif; line-height: 1.6; }

img { max-width: 100%; height: auto; display: block; }

.container { width: 100%; max-width: 1200px; margin: 0 auto; padding: 0 16px; }

@media (min-width: 768px) { html { font-size: 18px; } }

Progressive enhancement

Start with semantic HTML, enhance with CSS, add JavaScript for interactivity. This ensures the site works even if CSS or JS fails.