generate_website.py can layer custom CSS on top of the built-in style chosen with --style. --embed-css appends a local file to the page's <style> block so the page stays a single file, and --link-css adds a stylesheet link after it, so both override built-in rules of equal specificity. The flags can be combined (the linked stylesheet loads last), apply to --sample pages, and an unreadable --embed-css file stops generation with an error. The website docs gain a custom CSS guide and a reference for the generated page's structure, classes, and theme variables.
