← Prompts
Skill / Understand Web Quality Skills (Addy Osmani)

Best Practices

Apply modern web development best practices for security, compatibility, and code quality. Use when asked to "apply best practices", "security audit", "modernize code", "code quality review", or "check for vulnerabilities".

# Best practices

Modern web development standards based on Lighthouse best practices audits. Covers security, browser compatibility, and code quality patterns.

## Security

### HTTPS everywhere

**Enforce HTTPS:**
```html
<!-- ❌ Mixed content -->
<img src="http://example.com/image.jpg">
<script src="http://cdn.example.com/script.js"></script>

<!-- ✅ HTTPS only -->
<img src="https://example.com/image.jpg">
<script src="https://cdn.example.com/script.js"></script>

<!-- ✅ Protocol-relative (will use page's protocol) -->
<img src="//example.com/image.jpg">
```

**HSTS Header:**
```
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

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Classification

Skill Capability with explicit trigger pattern
Skill Understand
Explain or analyze
Scope Project
This codebase
Triggered Activates on context match -- file patterns, topics, working state