Senior HTML/CSS Developer – AI Training (Cambridge)

About the role

Prolific is seeking senior HTML/CSS developers to join its Expert Network and help train cutting‑edge AI models. After a short skills test, successful candidates will work as paid participants, reviewing and improving AI‑generated frontend code.

Key responsibilities

• Evaluate AI‑generated HTML/CSS for functional correctness, semantic structure and best‑practice compliance.
• Validate the logical explanations provided by the AI for layout and styling decisions.
• Execute rendering tests across browsers to verify visual output and cross‑browser behavior.
• Annotate model performance, highlighting inaccessible markup, inefficient selectors or deprecated properties.
• Provide structured feedback to refine the model’s reasoning on responsive design and component architecture.

Required profile

• BSc or higher in Computer Science, Software Engineering, Web Development or a related field.
• Proven senior‑level experience as a Frontend Developer or UI Engineer specializing in HTML/CSS.
• Strong ability to build complex, responsive layouts without relying on frameworks.
• Deep knowledge of CSS cascade, specificity, box model, Flexbox, CSS Grid, accessibility standards (WCAG) and cross‑browser compatibility.
• Commitment to clean, semantic markup and maintainable CSS following BEM methodology and design‑token standards.

Required skills

• HTML5, CSS3/4 (custom properties, animations, modern layout systems).
• Flexbox, CSS Grid, BEM, design tokens.
• Tailwind CSS, SASS/SCSS, CSS Modules.
• Browser DevTools, accessibility auditing tools such as axe or Lighthouse.
• Cross‑browser testing platforms.

What we offer

• Competitive hourly rate up to $40 per hour.
• Flexible, remote tasks that can be completed in one‑hour blocks.
• Opportunity to influence the development of advanced AI models.