Senior HTML/CSS Code Reviewer

About OpenTrain

OpenTrain is the #1 platform for building careers in AI training and data labeling. We connect skilled contributors with meaningful annotation work that directly shapes how next-generation AI systems behave. Creating an OpenTrain account is free.

About AI training work

AI training (also called data labeling or human feedback) is the human side of building intelligent systems. Annotators and reviewers produce high-quality examples and corrective feedback that models learn from — work that’s remote, flexible, and often accessible without prior AI experience.

This role focuses on code-response annotation: you’ll review and improve the labeled HTML/CSS data that trains design and front-end code models.

The Role

You will audit annotator reviews of AI-generated HTML/CSS snippets, verify correctness, and correct mis-ratings. This contractor role requires deep front-end expertise and clear written feedback to keep our labeling consistent with a strict quality rubric.

This is a part-time, remote contract (20+ hours/week), paid per hour at USD 23. Open to worldwide applicants who can provide professional-level written English.

What you’ll do

For each submission you’ll spin up a quick sandbox, validate that the code meets the prompt, and confirm rendering across breakpoints and browsers. You’ll check accessibility, performance, and security aspects, then correct labels and add concise, actionable feedback.

• Verify semantic HTML, ARIA usage, and SEO-friendly markup against the prompt.
• Test responsive layouts (Flexbox, Grid, container queries) across breakpoints.
• Validate accessibility against WCAG 2.2, ARIA patterns, and color-contrast rules.
• Assess performance (Web Vitals, critical CSS, lazy loading) and layout stability.
• Spot security issues like XSS, content injection, and clickjacking in markup/styles.
• Use automated tools (Lighthouse CI, axe-core, Playwright) and visual-diff checks (Percy, Chromatic).
• Correct mis-ratings, apply the quality rubric, and write clear, constructive feedback.

Requirements

You must have strong, proven front-end experience and be comfortable working in Dockerized sandboxes and modern build toolchains. Bring a quality-first mindset and excellent written English for feedback and mentoring.

• 7+ years professional front-end development, QA, or dedicated code-review experience focused on HTML and CSS.
• HTML5 mastery: semantic elements, ARIA roles, microdata, and SEO-friendly markup.
• CSS expertise: Flexbox, Grid, custom properties, logical properties, @layer, and container queries; experience with Sass or PostCSS.
• Responsive and cross-browser debugging skills for consistent rendering across devices.
• Accessibility leadership with strong knowledge of WCAG 2.2 and assistive-technology testing.
• Performance optimization experience: Web Vitals, critical CSS, minimizing layout shifts.
• Security awareness: identify and mitigate XSS, content-injection, and related markup risks.
• Familiarity with automated and visual testing tools: Lighthouse CI, axe-core, Playwright, Percy/Chromatic.
• Toolchain fluency: Docker, Vite/webpack, Git workflows, and code-review platforms (GitHub/GitLab).
• Excellent written English (approx. B2+ CEFR) for concise, constructive feedback and mentoring.

Nice to have

These extras help but are not required. Include them if you have experience that speeds up onboarding or improves review quality.

• Exposure to LLM evaluation or data-labeling workflows.
• Familiarity with design-system tools like Storybook or Figma.

Who should apply

Experienced front-end engineers, accessibility leads, senior QA engineers, and professional code reviewers who enjoy mentoring and improving annotation quality should apply. This role is ideal if you want flexible, remote work that directly influences how AI generates and evaluates front-end code.

How it works

OpenTrain hires and contracts contributors directly. After you apply and are accepted, you’ll receive onboarding to the labeling interface and quality rubric, plus examples and sandbox templates to speed up reviews. Work is remote and flexible; you’ll log hours as a contractor according to the project schedule.

• Schedule: part-time contract, 20+ hours/week.
• Compensation: USD 23 per hour, paid per the contract terms.
• Location: fully remote, worldwide.