HTML/CSS - Senior Developers - AI Training - Denver, USA

Prolific; Denver (CO); On-site; USD 45,460 - 64,747; Part time

Job summary

Prolific is seeking Senior HTML/CSS Developers in Denver, Colorado to join their Expert Network. In this role, you will help train AI models by reviewing and auditing generated code while earning competitive pay of up to $40/hr. Candidates should have a strong background in Software Engineering or Frontend Development, including expertise in creating responsive layouts and a deep knowledge of HTML and CSS standards. The position offers flexible working hours and the chance to contribute to cutting-edge technology.

Qualifications

• Proven experience as a Senior Frontend Developer or UI Engineer specializing in HTML/CSS.
• Ability to build complex, responsive layouts independently without frameworks.
• Expert understanding of the CSS cascade, box model, and Flexbox.

Responsibilities

• Review AI-generated HTML/CSS for functional correctness.
• Audit AI explanations for layout solutions and ensure technical soundness.
• Conduct execution testing of model-generated markup.

Skills

HTML/CSS mastery

Responsive layout implementation

Cross-browser compatibility

Semantic markup

BEM methodology

Accessibility standards

Education

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

Tools

Browser DevTools

Accessibility auditing tools

Cross-browser testing platforms

Job description

HTML/CSS - Senior Developers - AI Training - USA

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.

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 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 (axe, Lighthouse), and cross‑browser testing platforms.

Benefits

You can start in just 15 minutes, earning competitive pay rates up to $40/hr, with flexible hours and the ability to work from home.

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.