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

HTML/CSS - Senior Developers - AI Training - UK

About Prolific

Prolific is not just another player in the AI space – we are building the biggest pool of quality human data in the world.

Over 35,000 AI developers, researchers, and organizations use Prolific to gather data from paid study participants with a wide variety of experiences, knowledge, and skills.

The role

We're 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'll send you a quick 10- to 15-minute test to assess your skills. If successful, you'll be invited to join Prolific as a participant, where you'll get paid to help AI understand and produce high-quality frontend code and design implementation.

Researchers looking for your skills tend to pay up to $40/hr, depending on skills and experience. You must be prepared to complete paid tasks that require one hour of uninterrupted work, though many are shorter.

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 they are technically sound.
• 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 (e.g., axe, Lighthouse), and cross-browser testing platforms.

Why Prolific is a great platform to join as a Participant

Joining our platform as a Prolific participant will give you the chance to influence the AI models of the future using professional legal expertise. Once you pass our assessment, you can join Prolific in just 15 minutes, and start enjoying competitive pay rates, flexible hours, and the ability to work from home.

We've built a unique platform that connects researchers and companies with a global pool of participants, enabling the collection of high-quality, ethically sourced human behavioural data and feedback. This data is the cornerstone of developing more accurate, nuanced, and aligned AI systems.

We believe that the next leap in AI capabilities won't come solely from scaling existing models, but from integrating diverse human perspectives and behaviours into AI development. By providing this crucial human data infrastructure, Prolific is positioning itself at the forefront of the next wave of AI innovation – one that reflects the breadth and the best of humanity.

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By submitting your application, you agree that Prolific may collect your personal data for recruiting and global organisation planning. Prolific's Candidate Privacy Notice explains what personal information Prolific may process, where Prolific may process your personal information, its purposes for processing your personal information, and the rights you can exercise over Prolific use of your personal personal information.