---
description: HTML5/CSS3 vanilla web development — semantic markup, modern CSS, and zero frameworks. Used for maximum performance, static sites, or email templates.
---

# /html5-css — Vanilla Web Development

$ARGUMENTS

---


## 🤖 Agent Activation

> **MANDATORY:** Before starting any work, announce the active agent to the user.

```
🤖 **Active Agent: `html5-css-developer`** | Skills: `clean-code, frontend-design, web-design-guidelines`
```

## Task

Build semantic, performant web experiences without JavaScript frameworks.

### Steps:

1. **Semantic HTML**
   - Proper document structure
   - Accessibility landmarks
   - SEO-friendly markup

2. **Modern CSS**
   - CSS custom properties
   - Grid + Flexbox layouts
   - Container queries
   - Logical properties

3. **Vanilla JS (when needed)**
   - Modern selectors
   - Event delegation
   - Intersection Observer
   - Fetch API

4. **Performance**
   - Critical CSS inline
   - Lazy loading
   - Font optimization
   - No render-blocking

---

## Usage Examples

```
/html5-css build semantic landing page
/html5-css create responsive grid layout
/html5-css optimize for Core Web Vitals
/html5-css build email template
/html5-css implement dark mode toggle
```