html5-css-developer

html5-css-developer is a cursor rule for Cursor from MN-Lizard-Team/aiyu-multi-agent. It costs 76 tokens per session (2,279 once invoked), scanned A, original, Apache-2.0.

A coding guide for building websites with standard HTML, CSS, and JavaScript, without a framework or external dependencies. It emphasizes meaningful page structure, accessibility, and fast loading.

In plain words
What is it for?
Use it for landing pages, static websites, email templates, and other frontend work where minimal dependencies and performance matter.
Why use it?
It helps keep small web projects simple and avoids framework setup and runtime overhead. It also provides guidance for writing standards-based pages that work well for users and browsers.

Cursor rule for Cursor

Written for Cursor: installed under .cursor/. Also seen: mentions subagents; mentions Cursor.

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/mn-lizard-team/aiyu-multi-agent/html5-css-developer
Clone the repo
git clone --depth 1 https://github.com/MN-Lizard-Team/aiyu-multi-agent

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for html5-css-developer

README.md
[![agentmods](https://agentmods.dev/badge/rules/mn-lizard-team/aiyu-multi-agent/html5-css-developer.svg)](https://agentmods.dev/rules/mn-lizard-team/aiyu-multi-agent/html5-css-developer)
Your own site
<a href="https://agentmods.dev/rules/mn-lizard-team/aiyu-multi-agent/html5-css-developer"><img src="https://agentmods.dev/badge/rules/mn-lizard-team/aiyu-multi-agent/html5-css-developer.svg" alt="Measured on agentmods" height="20"></a>
Per session 76 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,279 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00076 $0.02279
Opus 5 $0.00038 $0.01140
Sonnet 5 $0.00015 $0.00456
Haiku 4.5 $0.00008 $0.00228

Measured 2d ago against content hash 1195635352d2, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

html5-css-developer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/agents/html5-css-developer.mdc · 350 lines

How it starts

The opening of the file, as written. The whole thing — 350 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Agent: html5-css-developer

Cursor Agent-Requested Rule — invoke via @html5-css-developer or let the AI auto-select.

Skills: clean-code, frontend-design, web-design-guidelines Tools: Read, Grep, Glob, Bash, Edit, Write, memory.save, memory.load Model: inherit Memory: session


🤖 Agent Identity

When this agent is activated, you MUST announce:

🤖 Active Agent: html5-css-developer | Skills: clean-code, frontend-design, web-design-guidelines | Rules: GEMINI, database-rules, deployment-rules, documentation-rules, performance-rules | Sub-agents: No

This announcement is MANDATORY — never skip it.


When to Activate

  • HTML5/CSS3 vanilla
  • semantic markup
  • modern CSS
  • maximum performance
  • static sites

HTML5/CSS Developer

Core Philosophy

  • Karpathy Principles: Think before coding, simplicity first, surgical changes, goal-driven execution

"Frameworks come and go. HTML, CSS, and JavaScript are the web. Master the fundamentals, understand the platform."

When to Go Vanilla

Situation Vanilla Framework
Landing page ✅ Fast, zero JS Overhead
Static site ✅ Perfect Unnecessary
Email template ✅ Required Doesn't work
Performance critical ✅ No bundle Parse + execute
Learning ✅ Fundamentals Abstractions
Complex SPA Painful React/Vue/Angular
Team of 5+ Hard to scale Framework helps

HTML5 Semantic Structure

<!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="Page description for SEO">
  <title>Semantic HTML5 Example</title>
  <link rel="stylesheet" href="styles.css">
</head>
<body>
  <header>
    <nav aria-label="Main navigation">
      <a href="/" aria-current="page">Home</a>
      <a href="/about">About</a>
    </nav>
  </header>
  
  <main>
    <article>
      <header>
        <h1>Article Title</h1>
        <time datetime="2024-01-15">January 15, 2024</time>
      </header>
      
      <section>
        <h2>Section Heading</h2>
        <p>Content with <strong>importance</strong> and <em>emphasis</em>.</p>
      </section>
      
      <aside>
        <h3>Related Links</h3>
        <ul>
          <li><a href="/related">Related article</a></li>
        </ul>
      </aside>
    </article>
  </main>
  
  <footer>
    <p>&copy; 2024 Company Name</p>
  </footer>
  
  <script src="app.js" type="module"></script>
</body>
</html>

Read the full file on GitHub · 350 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 350 lines · 76 tokens per session scan A 1195635352d2

Subscribe to this mod's changes

html5-css-developer is a cursor rule published in the GitHub repository MN-Lizard-Team/aiyu-multi-agent (7 stars, last pushed 3mo ago), licensed Apache-2.0. It adds 76 tokens to every session and 2,279 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.