Document Ansible-managed browser cache revalidation

README.md

@@ -113,6 +113,20 @@ The workflow requires these repository Actions secrets:
 The deployment deliberately excludes Git metadata, authoring documentation,
 the source GeoPackage, and other development-only files.
 
+## Browser caching
+
+The nginx server for `204.axvig.com` should send `Cache-Control: no-cache` so
+browsers revalidate HTML, modules, data, and images before reusing cached copies.
+ETag and Last-Modified responses still avoid downloading unchanged files.
+
+The policy is managed in the Ansible repository's
+`playbooks/static_sites/a_plot_of_plants.yml` through the `static_site_cache`
+tag. The static-site upload does not change nginx configuration.
+
+Verify the live response with `curl -I https://204.axvig.com/` and
+`curl -I https://204.axvig.com/src/main.js`; both should report
+`Cache-Control: no-cache`.
+
 ## Zoom behavior
 
 Both the yard overlays and the local basemap are vector data, so linework stays