web-conventions

web-conventions is a skill for Claude Code, Codex from AdamBien/airails. It costs 227 tokens per session (2,122 once invoked), scanned A, original, MIT.

A baseline set of HTML and CSS rules for web frontends, including meaningful markup, accessibility, responsive styling, design tokens, and browser support. It is meant to be combined with more specific frontend rules.

In plain words
What is it for?
Use it when writing or reviewing HTML and CSS for a website or web application, especially when choosing semantic elements, accessibility behavior, responsive styles, or reusable design values.
Why use it?
It provides shared standards for making web pages understandable, usable, and consistent across projects. It also clarifies which concerns belong in separate rules for JavaScript, static sites, or web applications.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

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 skills/adambien/airails/web-conventions
Any agent
npx skills add AdamBien/airails --skill web-conventions
Clone the repo
git clone --depth 1 https://github.com/AdamBien/airails

Made for: Claude Code, Codex.

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 web-conventions

README.md
[![agentmods](https://agentmods.dev/badge/skills/adambien/airails/web-conventions.svg)](https://agentmods.dev/skills/adambien/airails/web-conventions)
Your own site
<a href="https://agentmods.dev/skills/adambien/airails/web-conventions"><img src="https://agentmods.dev/badge/skills/adambien/airails/web-conventions.svg" alt="Measured on agentmods" height="20"></a>
Per session 227 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,122 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 $0.00227 $0.02122
Opus 5 $0.00113 $0.01061
Sonnet 5 $0.00045 $0.00424
Haiku 4.5 $0.00023 $0.00212

Measured 6d ago against content hash fed7c4b321d9, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

web-conventions 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 6d 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.

web/web-conventions/SKILL.md · 105 lines

How it starts

The opening of the file, as written. The whole thing — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Apply all rules below strictly to any HTML and CSS you write, generate, or review.

Scope

  • Platform-level rules for HTML and CSS only — semantics, accessibility, styling, theming, browser-support policy.
  • JavaScript language-level rules — modules, syntax, functions, collections, asynchrony, errors, JSDoc types — are not in this skill; they are the sibling baseline javascript-conventions, which applies the Baseline policy below to JavaScript syntax and APIs.
  • JavaScript policy (whether JavaScript is used at all), architecture, state management, routing, dependencies, project structure, and verification loops are not in this skill — see the context-specific skills web-static (no-JavaScript static sites), web-sprinkles (static sites with bounded JavaScript enhancements), and web-components (web component SPAs).
  • Responsive strategy (media queries vs container queries) is stack-specific — the composed skill decides.
  • When a composed skill specifies a rule, the composed skill wins; this skill is the fallback baseline.

Guiding Principles

  • web standards and web platform first
  • minimal external dependencies — every dependency must justify its existence
  • progressive enhancement over JavaScript-first design

HTML Rules

  • semantic elements over generic <div>/<span> — use <header>, <nav>, <main>, <article>, <section>, <aside>, <footer>, <figure>, <time>, <address>
  • one <main> per page
  • proper heading hierarchy (h1 → h2 → h3, no skipping)
  • lang attribute on <html>
  • alt on all images (empty alt="" for decorative)
  • aria-label on <nav> when multiple navs exist
  • <label> associated with every form input
  • skip link for keyboard users
  • use <a> for navigation, not buttons
  • use <br> only for line breaks in content, never for spacing

Form Rules

  • use the semantically correct input type — email, url, tel, password, search, number, date, time, range, file, checkbox, radio — never type="text" plus JavaScript re-implementation; the type alone provides the right mobile keyboard, native widget, and built-in validation (all Widely Available)
  • exception: <input type="color"> is Baseline Limited — do not use it; fall back to a text input with a pattern for hex colors
  • declare constraints in markup: required, pattern, min/max/step, minlength/maxlength — built-in validation is the first line of defense, JavaScript only for rules markup cannot express (Constraint Validation API is Widely Available)
  • autocomplete on every field with a well-known meaning (name, email, street-address, current-password, …) — autofill is both UX and accessibility
  • inputmode only when no dedicated input type fits (Widely Available)
  • placeholder is a hint, never a substitute for a <label>
  • group related controls with <fieldset>/<legend>
  • give every <button> inside a form an explicit type — the default is submit, which makes stray buttons submit the form
  • style validation states with :user-valid/:user-invalid (Widely Available since 2026-05), not :valid/:invalid — the :user-* pseudo-classes wait for user interaction instead of flagging pristine fields

Read the full file on GitHub · 105 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 6d ago First seen · 105 lines · 227 tokens per session scan A fed7c4b321d9

Subscribe to this mod's changes

web-conventions is a skill published in the GitHub repository AdamBien/airails (48 stars, last pushed yesterday), licensed MIT. It adds 227 tokens to every session and 2,122 once invoked, about $0.0011 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 2026-08-30.

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