Senior HTML/CSS Code Reviewer

About OpenTrain

OpenTrain is the #1 platform for finding and building careers in AI training and data labeling. We connect people with projects that help teach AI systems how to behave, and we support contributors who want flexible, remote work at the center of modern AI development.

Why AI training work matters

AI training (also called data labeling or human feedback) is the human side of building AI: models learn from examples and quality checks that people prepare and review. Contributors help shape how state-of-the-art design tools behave and can do this work remotely and flexibly while gaining valuable domain experience.

• 100% remote: work from anywhere with a computer and internet connection.
• Flexible, part-time friendly: this contract is compatible with other commitments.
• Impactful: your reviews and feedback directly improve AI design outputs.

The role

You will audit annotator reviews of AI-generated HTML/CSS snippets to ensure accuracy and adherence to our quality rubric. This is a remote, contract, part-time role requiring 20+ hours per week. Pay is $23 USD per hour. You will validate whether submissions meet the prompt, render correctly across breakpoints, follow accessibility and security best practices, and avoid common anti-patterns.

• Employment type: Contractor, Part-time.
• Schedule: 20+ hours/week (remote, worldwide).
• Compensation: $23 USD per hour, paid per hour.

What you'll do day-to-day

Your core task is to spin up quick sandboxes, inspect AI-generated code, reproduce issues, and confirm that annotator ratings match reality. You will correct mis-ratings, write concise feedback for annotators, and document recurring problems so the team can improve guidelines and tooling.

• Verify that code meets the original prompt and functional expectations across breakpoints.
• Check semantic markup, ARIA roles, and SEO-friendly structure.
• Evaluate CSS for performance, maintainability, and modern techniques (Flexbox, Grid, custom properties, container queries, @layer).
• Spot accessibility violations per WCAG 2.2 and recommend fixes.
• Identify security risks in markup and styling (XSS, content injection, clickjacking).
• Use automated and manual tools to validate results and produce clear reviewer comments.

Requirements

You must have substantial, demonstrable front-end experience and be able to provide clear, constructive feedback in English. Preserve high standards: your reviews will be used to train AI systems and improve annotation quality.

• 7+ years professional experience in front-end development, QA, or dedicated code-review roles focused on HTML and CSS.
• HTML5 mastery: semantic elements, ARIA roles, microdata, and SEO-friendly markup.
• CSS expertise with modern features: Flexbox, Grid, custom properties, logical properties, container queries, @layer, and preprocessors (Sass, PostCSS).
• Responsive & cross-browser skills: craft fluid, breakpoint-driven layouts that render consistently across modern browsers and devices.
• Accessibility leadership: solid grasp of WCAG 2.2, ARIA patterns, color-contrast rules, and assistive-technology testing.
• Performance optimization knowledge: Web Vitals, critical CSS, lazy loading, and minimizing layout shifts.
• Security awareness: ability to spot and mitigate XSS, content-injection, and clickjacking risks in markup and styles.
• Testing & validation experience with tools such as Lighthouse CI, axe-core, Playwright, and visual-diff platforms (Percy, Chromatic).
• Toolchain fluency: comfortable with Dockerized environments, Vite or webpack, and version-control review workflows (GitHub/GitLab PRs).
• Excellent written English (B2+ CEFR) for clear, concise feedback and mentoring.

Nice to have

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

How the work is evaluated

You will follow a defined quality rubric when auditing annotations. Accuracy of your corrections, clarity of your feedback, and consistency with rubric standards are the main performance indicators. Expect to use a mix of quick local sandboxes and automated checks to validate submissions.

• Correctness and alignment with the prompt and rubric.
• Clarity and usefulness of written feedback to annotators.
• Consistent application of accessibility, performance, and security best practices.

How to apply

If this role matches your background, prepare examples or references that demonstrate your HTML/CSS review experience and accessibility work. OpenTrain will guide you through a short evaluation to verify technical skills and review consistency. Creating an OpenTrain account is free and is the first step to apply.