Imported from rondoflow/rondoflow (
packages/catalog/content/skills/build-seo-friendly-websites/SKILL.md). Install upstream withnpx skills add rondoflow/rondoflow --skill build-seo-friendly-websites. Copyright stays with the author.
Website Development Rules
Performance
- Images are the #1 cause of slow sites — use WebP/AVIF, lazy-load below-the-fold, and set explicit width/height to prevent layout shift
- Render-blocking CSS delays first paint — inline critical CSS in
<head>, defer the rest - Third-party scripts (analytics, chat widgets) often add 500ms+ — load them with
asyncordefer, audit regularly - Fonts cause invisible text flash (FOIT) — use
font-display: swapand preload critical fonts - Measure with Lighthouse in incognito mode — extensions skew results
Mobile First
- Start CSS with mobile styles, add complexity with
min-widthmedia queries — easier to scale up than strip down - Touch targets need 44x44px minimum — fingers are imprecise, small buttons frustrate users
- Test on real devices, not just browser DevTools — throttling simulation misses real-world jank
- Horizontal scroll is a critical bug — test every page at 320px width minimum
viewportmeta tag is required:<meta name="viewport" content="width=device-width, initial-scale=1">
Accessibility
- Every
<img>needsalttext — emptyalt=""for decorative images, descriptive text for meaningful ones - Color contrast ratio 4.5:1 minimum for body text — use WebAIM contrast checker
- Form inputs must have associated
<label>elements — placeholders alone are not accessible - Keyboard navigation must work — test every interactive element with Tab key
- Screen readers announce heading hierarchy — use H1-H6 in logical order, never skip levels
HTML Structure
- One
<h1>per page only — it's the page title, not a styling tool - Use semantic elements:
<nav>,<main>,<article>,<aside>,<footer>— they communicate structure to browsers and assistive tech <button>for actions,<a>for navigation — don't use divs with click handlers- External links should have
rel="noopener"— prevents security vulnerability withtarget="_blank" - Validate HTML — broken markup causes unpredictable rendering across browsers
CSS Patterns
- Avoid
!important— it breaks cascade and makes debugging painful. Fix specificity instead - Use relative units (
rem,em,%) over fixedpxfor text — respects user font size preferences - CSS custom properties (variables) reduce repetition — define colors and spacing once, use everywhere
- Flexbox for 1D layouts, Grid for 2D — don't force one to do the other's job
- Test without CSS loading — content should still be readable in plain HTML
Common Mistakes
- Missing favicon causes 404 spam in server logs — always include one, even a simple PNG
- Not setting
<html lang="en">breaks screen reader pronunciation - Hardcoded
http://links break on HTTPS sites — use protocol-relative//or alwayshttps:// - Assuming JavaScript is available — core content should work without JS (progressive enhancement)
- Forgetting print styles — add
@media printfor pages users might print (receipts, articles)
Before Launch
- Test all forms actually submit — broken contact forms lose leads silently
- Check 404 page exists and is helpful — default server 404 looks unprofessional
- Verify social sharing previews with Open Graph tags — test in Facebook/Twitter debuggers
- Submit sitemap to Google Search Console — speeds up indexing
- Set up uptime monitoring — know when your site goes down before users tell you