A CSS file does not need a special type of hosting. It is a static asset: include it in the published ZIP, link to it with the correct URL, and confirm the server returns the stylesheet instead of an error page. Most CSS failures come from a wrong path, different filename capitalization, or an archive that omitted the file.

Use a predictable file structure

index.html
about/index.html
assets/css/site.css
assets/js/app.js
assets/images/logo.svg

From the home page, link the stylesheet with <link rel="stylesheet" href="assets/css/site.css">. From about/index.html, use ../assets/css/site.css. Root-relative URLs such as /assets/css/site.css are fine only when the site always lives at the domain root; relative URLs are more portable for previews and subdirectories.

Never reference your local machine

Wrong: href="C:\\Users\\me\\site\\site.css"
Wrong: href="file:///Users/me/site/assets/css/site.css"
Right: href="assets/css/site.css"

A visitor cannot retrieve a file from your laptop. The stylesheet must be in the uploaded archive at the path your HTML requests.

Debug an unstyled page

  1. View page source and copy the stylesheet URL from the link tag.
  2. Open that URL directly. It should show CSS text, not an HTML error document.
  3. Open DevTools → Network, reload with cache disabled, and filter for CSS.
  4. A 404 means the URL does not match the archive path. A 200 response containing HTML often means a fallback page was returned instead.
  5. Check capitalization exactly: Styles.css and styles.css are different on most production servers.

Publish CSS responsibly

  • Keep one main stylesheet on small sites; split files only when a real page or component boundary benefits.
  • Minify production CSS with your build tool, but retain readable source locally.
  • Use a content-hashed or versioned filename for changed stylesheets to reduce stale-cache issues.
  • Never put secrets in CSS comments or custom properties: public CSS is downloadable by anyone.

The MDN link-element reference explains the browser-side stylesheet relationship and optional attributes such as media.