HTML Standards & Best Practices

HTML Living Standard

WHATWG HTML Living Standard

The HTML Living Standard is the authoritative specification for HTML, maintained by WHATWG (Web Hypertext Application Technology Working Group).

Semantic HTML

Use HTML elements according to their intended meaning:

  • <header>: Site/page header content
  • <nav>: Navigation menus
  • <main>: Primary page content
  • <article>: Self-contained content
  • <section>: Thematic groupings
  • <aside>: Sidebar content
  • <footer>: Site/page footer
Valid HTML

Ensure HTML follows standards and validates:

  • Proper nesting: Elements closed in correct order
  • Unique IDs: No duplicate ID attributes
  • Required attributes: Alt text for images
  • Proper DOCTYPE: <!DOCTYPE html>
  • Valid attributes: Use only defined attributes
  • Character encoding: UTF-8 declaration

Document Structure Standards

Essential HTML Document Elements

Minimal HTML5 Document
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Page Title</title>
</head>
<body>
    <header role="banner">
        <h1>Site Title</h1>
        <nav role="navigation">...</nav>
    </header>
    <main role="main">
        <h1>Page Heading</h1>
        <p>Content...</p>
    </main>
    <footer role="contentinfo">...</footer>
</body>
</html>
SEO Essentials
  • Title tag: Descriptive, unique titles
  • Meta description: Page summaries
  • Heading hierarchy: Logical H1-H6 structure
  • Alt attributes: Image descriptions
  • Lang attribute: Document language
  • Canonical URLs: Prevent duplicate content

HTML Accessibility Standards

ARIA and Semantic Elements
  • Landmark roles: banner, navigation, main, contentinfo
  • ARIA labels: aria-label, aria-labelledby, aria-describedby
  • ARIA states: aria-expanded, aria-hidden, aria-live
  • Form associations: Label elements with for attribute
  • Focus management: Logical tab order
Keyboard Navigation
  • Focusable elements: Links, buttons, form controls
  • Skip links: Jump to main content
  • Tabindex usage: Control focus order (-1, 0, positive)
  • Focus indicators: Visible focus styles
  • Logical flow: Reading order matches visual order

Form Elements & Input Standards

Accessible Forms are Essential

Forms must be usable by everyone, including people using assistive technologies.

Form Best Practices

  • Label association: Every input has a label element
  • Required field indication: Use required attribute and visual indicators
  • Error messaging: Clear, specific error descriptions
  • Fieldset grouping: Related form controls grouped with legend
  • Input types: Use semantic input types (email, tel, url, date)
  • Autocomplete attributes: Help users fill forms faster
Form Example
<form>
  <fieldset>
    <legend>Contact Information</legend>
    
    <label for="email">Email Address *</label>
    <input type="email" id="email" name="email" 
           required aria-describedby="email-error"
           autocomplete="email">
    <div id="email-error" role="alert"></div>
    
    <label for="phone">Phone Number</label>
    <input type="tel" id="phone" name="phone"
           autocomplete="tel">
  </fieldset>
  
  <button type="submit">Submit</button>
</form>

HTML Performance Optimization

Resource Loading
Optimize Resource Loading:
  • Preload critical resources: <link rel="preload">
  • Defer non-critical scripts: defer, async attributes
  • Lazy load images: loading="lazy" attribute
  • Optimize images: WebP format, responsive images
  • Minimize DNS lookups: Reduce external domains
Responsive Images
Responsive Image Techniques:
  • srcset attribute: Multiple image sizes
  • picture element: Art direction and format selection
  • sizes attribute: Image size hints
  • width/height attributes: Prevent layout shift
  • Modern formats: WebP, AVIF with fallbacks

Modern HTML5 APIs

Web Storage

localStorage and sessionStorage for client-side data persistence

Geolocation

Access user's geographic location with proper permission handling

Notifications

Push notifications and background sync capabilities

HTML Validation and Testing

Validation Tools
  • W3C Markup Validator: Official HTML validation service
  • HTML5 Validator: Check HTML5 specific features
  • Browser DevTools: Built-in validation and debugging
  • Automated testing: Include validation in CI/CD pipelines
Testing Strategies
  • Cross-browser testing: Multiple browsers and versions
  • Accessibility testing: Screen readers, keyboard navigation
  • Performance testing: Core Web Vitals, loading times
  • Mobile testing: Various devices and screen sizes
HTML Standards Checklist
Structure & Semantics
Accessibility & Performance

Improve HTML Standards Compliance

Report HTML standards violations and access resources for better markup practices.

Report HTML Issue HTML Resources Standards Guide