HTML​/CSS - Senior Developers - AI Training - Sheffield, UK

Contribute senior frontend expertise to paid tasks that train and evaluate AI systems' ability to produce reliable HTML and CSS. Work involves reviewing generated code and explanations, checking rendered results, and giving structured feedback; tasks may require up to an hour of uninterrupted work.

• Assess generated markup and styles for correctness, semantic structure, and maintainability.
• Check whether explanations of layout and styling decisions are technically sound.
• Render code and inspect its appearance and behavior across browsers.
• Flag accessibility problems, inefficient selectors, deprecated markup, and invalid CSS.
• Give feedback on responsive layouts, component structure, and design system reasoning.

• A bachelor's degree or higher in computer science, software engineering, web development, or a related field.
• Professional experience as a senior frontend developer or UI engineer focused on HTML and CSS.
• Ability to build complex responsive layouts and components independently, including without frameworks.
• Strong knowledge of the CSS cascade, specificity, box model, Flexbox, Grid, accessibility standards, and browser compatibility.
• Skilled in producing semantic HTML and maintainable CSS, with familiarity with BEM, design tokens, and modern standards.
• Proficiency with HTML5 and modern CSS, plus browser developer tools and accessibility or cross-browser testing tools.

• Experience with Tailwind CSS, Sass/SCSS, CSS Modules, or component-based design systems.
• Familiarity with CSS custom properties, animations, and modern layout techniques.

• Remote participation with flexible hours; tasks vary in length, and some require an uninterrupted hour.
• Paid tasks may offer up to $40 per hour depending on skills and experience.
• Applicants complete a 10-15 minute skills assessment before being invited to participate.