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Guidelines for writing HTML that is accessible, semantic, maintainable, and secure. Use when working with .html, .vue, .twig, .php, .cshtml, .svelte files, or when the user asks about HTML structure, semantic markup, accessibility, or web security best practices.
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SOC 職業分類に基づく
Standards for writing clear and consistent commit messages using Conventional Commits format. Use when making git commits, reviewing commit history, creating pull requests, or when the user asks about commit message formatting, git workflows, or version control best practices.
C# coding standards and conventions including naming, formatting, and best practices. Use when working with .cs files, writing C# code, or when the user asks about C# naming conventions, code structure, XML documentation, or .NET development patterns.
Guidelines for writing CSS that is simple, readable, and maintainable. Use when working with .css, .scss, .sass files, CSS-in-JS, styled-components, or when the user asks about CSS organization, selectors, specificity, reusability, performance, or responsive design patterns.
.NET coding standards and conventions including project structure, dependency injection, and best practices. Use when working with .NET projects, ASP.NET Core, or when the user asks about .NET architecture, dependency injection, async patterns, or project organization.
Guidelines for writing JavaScript and TypeScript code that is simple, readable, and maintainable. Use when working with .js, .jsx, .ts, .tsx, .mjs, .cjs files, or when the user asks about JavaScript/TypeScript coding standards, ES2022 features, Node.js modules, async/await patterns, or testing with Vitest.
Documentation and content creation standards for Markdown files. Use when creating or editing .md files, writing documentation, README files, or when the user asks about Markdown formatting, content structure, front matter, or documentation best practices.
| name | html-standards |
| description | Guidelines for writing HTML that is accessible, semantic, maintainable, and secure. Use when working with .html, .vue, .twig, .php, .cshtml, .svelte files, or when the user asks about HTML structure, semantic markup, accessibility, or web security best practices. |
| metadata | {"author":"devbyray","version":"1.0","languages":"html, html5"} |
Apply these standards when writing HTML markup to ensure accessibility, semantics, maintainability, and security.
Prefer semantic elements over generic divs and spans:
Good:
<header>
<nav>
<ul>
<li><a href="/">Home</a></li>
</ul>
</nav>
</header>
<main>
<article>
<h2>Article Title</h2>
<section>
<p>Content...</p>
</section>
</article>
<aside>
<h3>Related Links</h3>
</aside>
</main>
<footer>
<p>© 2026 Company Name</p>
</footer>
Bad:
<div class="header">
<div class="nav">...</div>
</div>
<div class="main">
<div class="article">...</div>
</div>
Always use proper HTML5 document structure:
<!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>
<!-- Content -->
</body>
</html>
<h1> (reserved for page title generation)Good:
<h2>Main Section</h2>
<h3>Subsection</h3>
<h4>Detail</h4>
Bad:
<h1>Title</h1>
<!-- Don't use H1 -->
<h4>Content</h4>
<!-- Skipped H2, H3 -->
All images must have descriptive alt text:
<!-- Informative image -->
<img src="chart.png" alt="Sales chart showing 20% increase in Q4 2025" />
<!-- Decorative image -->
<img src="divider.png" alt="" />
Always label form controls:
<form>
<label for="email">Email address</label>
<input type="email" id="email" name="email" required />
<label for="password">Password</label>
<input type="password" id="password" name="password" required />
<button type="submit">Submit</button>
</form>
Ensure interactive elements are keyboard accessible:
<button type="button">Clickable Button</button>
<a href="/page">Link to Page</a>
<!-- Only use tabindex="0" for custom interactive elements -->
<div role="button" tabindex="0" onclick="handleClick()">Custom Button</div>
Use ARIA only when native HTML is insufficient:
<!-- Good: Native HTML -->
<button>Click me</button>
<!-- OK: ARIA when needed -->
<button aria-label="Close dialog">×</button>
<!-- Good: ARIA for custom widgets -->
<div role="dialog" aria-labelledby="dialog-title" aria-modal="true">
<h2 id="dialog-title">Dialog Title</h2>
</div>
Keep HTML clean by using external files:
Bad:
<div style="color: red; font-size: 20px;" onclick="alert('clicked')">Content</div>
Good:
<div class="error-text" data-action="show-alert">Content</div>
Use lowercase, hyphen-separated names:
<div class="main-header"></div>
<nav class="site-navigation"></nav>
<button id="submit-button">Submit</button>
Use comments to organize sections:
<!-- Header Section -->
<header>
<!-- Navigation -->
<nav>...</nav>
</header>
<!-- Main Content -->
<main>...</main>
Never inject raw user data into the DOM:
Bad (XSS vulnerability):
element.innerHTML = userInput
Good:
element.textContent = userInput
// OR use DOMPurify for HTML
element.innerHTML = DOMPurify.sanitize(userInput)
Include security headers:
<head>
<meta charset="UTF-8" />
<meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self' 'unsafe-inline'" />
<meta http-equiv="X-Content-Type-Options" content="nosniff" />
<meta http-equiv="Strict-Transport-Security" content="max-age=31536000; includeSubDomains" />
</head>
<!-- Modern formats with fallback -->
<picture>
<source srcset="image.webp" type="image/webp" />
<source srcset="image.jpg" type="image/jpeg" />
<img src="image.jpg" alt="Description" loading="lazy" />
</picture>
<!-- Lazy loading for non-critical images -->
<img src="image.jpg" alt="Description" loading="lazy" />
Use preload and prefetch for critical resources:
<head>
<!-- Preload critical CSS -->
<link rel="preload" href="critical.css" as="style" />
<!-- Prefetch next page -->
<link rel="prefetch" href="/next-page" />
<!-- DNS prefetch for external domains -->
<link rel="dns-prefetch" href="https://api.example.com" />
</head>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="description" content="Brief page description for SEO" />
<meta http-equiv="Content-Security-Policy" content="default-src 'self'" />
<title>Page Title - Site Name</title>
<link rel="preload" href="styles.css" as="style" />
<link rel="stylesheet" href="styles.css" />
</head>
<body>
<!-- Header -->
<header class="site-header">
<nav class="main-navigation" aria-label="Main navigation">
<ul>
<li><a href="/" aria-current="page">Home</a></li>
<li><a href="/about">About</a></li>
<li><a href="/contact">Contact</a></li>
</ul>
</nav>
</header>
<!-- Main Content -->
<main id="main-content">
<article>
<h2>Article Title</h2>
<section>
<h3>Section Heading</h3>
<p>Content paragraph with <a href="/link">descriptive link text</a>.</p>
<img src="image.jpg" alt="Detailed description of the image" loading="lazy" />
</section>
<section>
<h3>Form Section</h3>
<form action="/submit" method="post">
<label for="name">Full Name</label>
<input type="text" id="name" name="name" required />
<label for="email">Email Address</label>
<input type="email" id="email" name="email" required />
<button type="submit">Send</button>
</form>
</section>
</article>
<aside class="sidebar">
<h3>Related Content</h3>
<ul>
<li><a href="/related-1">Related Article 1</a></li>
<li><a href="/related-2">Related Article 2</a></li>
</ul>
</aside>
</main>
<!-- Footer -->
<footer class="site-footer">
<p>© 2026 Company Name. All rights reserved.</p>
</footer>
<script src="app.js" defer></script>
</body>
</html>
Apply these standards when: