HTML + CSS + Javascript-HTML CSS JavaScript toolkit

Example

```html <header> <h1>City Library</h1> <nav aria-label='Primary'> <a href='/catalog'>Catalog</a> <a href='/events'>Events</a> </nav> </header> <main> <article> <h2>New Arrivals</h2> <p>Discover the latest books in our collection.</p> </article> <form id='signup' aria-labelledby='signup-title'> <h3 id='signup-title'>Get updates</h3> <label>Email <input type='email' name='email' required></label> <button type='submit'>Subscribe</button> </form> </main> <footer>&copy; 2025 City Library</footer> ```

Scenario

Content-heavy sites (news, documentation, blogs) rely on semantic HTML to improve SEO, accessibility (screen readers understand landmarks like <header>, <nav>, <main>), and maintainability. Forms with proper input types and attributes (required, type='email') give built-in validation and mobile-friendly keyboards without any JavaScript.

Example

```css :root { --brand: #0ea5e9; --bg: #0b1020; --text: #e5e7eb; } @media (prefers-color-scheme: dark) { body { background: var(--bg); color: var(--text); } } .container { display: grid; grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr)); gap: 1rem; } .card { border: 1px solid rgba(14,165,233,.3); border-radius: .75rem; padding: 1rem; } @media (max-width: 768px) { .sidebar { display: none; } } ```

Scenario

A marketing site needs to look great on phones, tablets, and desktops. CSS Grid and Flexbox deliver fluid layouts; custom properties (variables) implement design tokens for consistent theming; media queries adapt UI to screen size and user preferences (dark mode). Teams ship faster by keeping HTML stable while iterating on CSS to redesign pages or run A/B tests.

Example

```js const list = document.querySelector('#news'); async function load() { const res = await fetch('https://api.example.com/news'); const items = await res.json(); list.innerHTML = items.map(i => `<li>${i.title}</li>`).join(''); } document.querySelector('#refresh').addEventListener('click', load); load(); ```

Scenario

Dashboards, ecommerce carts, and SaaS apps fetch data from APIs, manage client-side state, and update the DOM without full page reloads. JavaScript powers features like auto-saving forms, live search, drag-and-drop, real-time notifications, offline-first PWAs, and access to device capabilities (clipboard, geolocation, camera—with permissions).