# Frontend Coding Standards > Front-end entry point for systemprompt.io — HTML standards, progressive enhancement doctrine, asset registration, and performance requirements. Routes to javascript-coding-standards and css-coding-standards, which are canonical for their languages. - Skill: `systempromptio/frontend-coding-standards` (Agent Skill) - Install (CLI): `npx skillmds@latest add systempromptio/frontend-coding-standards` - Raw SKILL.md: https://api.skillmd.com/api/skills/systempromptio/frontend-coding-standards/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Web & Frontend - Author: systempromptio (https://skillmd.com/u/systempromptio) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/systempromptio/frontend-coding-standards --- # Front-End Coding Standards HTML standards and the front-end delivery workflow for systemprompt.io. Follow without exception. ## Where the rules live This skill no longer carries JavaScript or CSS rules. Each language has one canonical source of truth, so a review can cite a rule instead of arguing with a second copy of it. | Subject | Skill | |---------|-------| | JavaScript — modules, rendering architectures, state, forbidden constructs | `javascript-coding-standards` | | CSS — tokens, BEM, forbidden constructs, file limits | `css-coding-standards` | | **HTML, progressive enhancement, asset registration, performance** | **this skill** | | Colour science, typography scale, elevation | `visual-design-system` | | Component recipes (cards, tables, forms, dashboards) | `component-patterns` | | Container queries, `:has()`, subgrid, view transitions | `modern-css-patterns` | | Micro-interactions, skeleton UI, motion choreography | `ux-interaction-patterns` | | PDF factsheets and print one-pagers | `factsheet-design` | ## Core Principle systemprompt.io uses progressive enhancement with static HTML/CSS and minimal vanilla JavaScript. Every front-end file must be modular, framework-free, and enhance -- never replace -- server-rendered content. CSS-only solutions are always preferred over JavaScript. No frameworks, no build tools, no transpilation. ## Language Separation Principle **JavaScript files contain only JavaScript. CSS belongs in `.css` files or `CSSStyleSheet` objects. HTML belongs in templates, in `