What is a style guide in web development?

A style guide in web development serves as a comprehensive document that establishes the visual and design standards for a website. This guide typically includes specifications on typography, color palettes, layout grids, and image usage, ensuring that all design elements are consistent across different pages of the site. By adhering to a style guide, designers and developers can create a cohesive user experience that aligns with the overall brand identity. This consistency is crucial for usability and can enhance user trust and engagement.

In contrast, the other options focus on different aspects of web development. A manual for writing code emphasizes coding standards and practices, which although important, is distinct from the visual design elements covered in a style guide. A checklist for testing website functionality pertains to ensuring that a site operates correctly and efficiently, while a guideline for SEO best practices focuses on optimizing a website for search engine visibility. While all these elements are important parts of web development, they do not specifically encompass the visual and design standards that a style guide addresses.