HTML/CSS - Senior Developers - AI Training - Colchester, UK

Prolific; Colchester; On-site; GBP 30,567 - 50,946; Part time

Job summary

Prolific is seeking a Senior HTML/CSS Developer to join their Expert Network in the UK. In this role, you'll evaluate and review AI-generated frontend code while bringing forth your real-world experience in Software Engineering. Responsibilities include ensuring functional correctness, conducting execution testing, and providing structured feedback on model performance. Successful candidates can earn up to $40/hour, depending on their skills and experience, with tasks often requiring as little as one hour of work.

Qualifications

• Real-world experience as a Senior Frontend Developer or UI Engineer specializing in HTML/CSS.
• Expert understanding of the CSS cascade, specificity, the box model, Flexbox, and CSS Grid.

Responsibilities

• Review AI-generated HTML/CSS for functional correctness and semantic structure.
• Audit step-by-step explanations from AI for layout solutions to ensure technical soundness.
• Render model-generated markup and stylesheets to verify visual output and cross-browser behavior.

Skills

Expert mastery of HTML5 and CSS3/4

Ability to build complex, responsive layouts

Proficiency with browser DevTools

Education

BSc or higher in Computer Science, Software Engineering, or related field

Tools

Tailwind CSS

SASS/SCSS

Accessibility auditing tools (axe, Lighthouse)

Job description

HTML/CSS - Senior Developers - AI Training - UK

The role

We are looking for Senior HTML/CSS Developers to join our Expert Network to help train and evaluate cutting‑edge AI models. If you have a background in Software Engineering or Frontend Development, we will test your skills with a short assessment. Successful candidates will participate in paid tasks that involve writing and reviewing high‑quality frontend code and design implementation.

What you’ll bring

• Educational Background: a BSc or higher in Computer Science, Software Engineering, Web Development, or a closely related technical field.
• Professional Experience: real‑world experience as a Senior Frontend Developer or UI Engineer specialising in HTML/CSS.
• Coding Proficiency: ability to independently build complex, responsive layouts and components without relying on frameworks or libraries.
• Deep Domain Knowledge: expert understanding of the CSS cascade, specificity, the box model, Flexbox, CSS Grid, accessibility standards (WCAG), and cross‑browser compatibility.
• Code Quality: a high standard for clean, semantic markup and maintainable CSS, including adherence to BEM methodology, design tokens, and modern CSS standards.

What you’ll be doing in the role

• Evaluate Code Accuracy: review AI‑generated HTML/CSS for functional correctness, semantic structure, and adherence to best practices.
• Validate Logic & Reasoning: audit the step‑by‑step explanations provided by AI for layout solutions and styling approaches to ensure technical soundness.
• Conduct Execution Testing: render model‑generated markup and stylesheets in appropriate environments to verify visual output and cross‑browser behaviour.
• Annotate Model Performance: identify areas where a model produces inaccessible markup, inefficient selectors, deprecated attributes, or hallucinated CSS properties.
• Refine Technical Logic: provide structured feedback on how models reason through responsive design, component architecture, or design system implementation.

Key Technologies

• Core Languages: expert mastery of HTML5 and CSS3/4, including custom properties, animations, and modern layout systems.
• Frameworks & Methodologies: extensive experience with Tailwind CSS, SASS/SCSS, or CSS Modules, and familiarity with component‑driven design systems.
• Testing & Tools: proficiency with browser DevTools, accessibility auditing tools (axe, Lighthouse), and cross‑browser testing platforms.

Remuneration

Researchers typically offer up to $40/hr, depending on skills and experience. Tasks require one hour of uninterrupted work, though many are shorter.