Update pages docs with info about geo setup

doc/administration/pages/index.md

@@ -1263,6 +1263,14 @@ For example, you can adapt the `rsync` strategy from the
 [moving repositories documentation](../operations/moving_repositories.md).
 Alternatively, run the CI pipelines of those projects that contain a `pages` job again.
 
+## 404 or 500 error when accessing GitLab Pages in a Geo setup
+
+Pages sites are only available on the primary Geo site, while the codebase of the project is available on all sites. 
+
+If you try to access a Pages page on a secondary site, you will get a 404 or 500 HTTP code depending on the access control.
+
+Read more which [features don't support Geo replication/verification](../geo/replication/datatypes.md#limitations-on-replicationverification).
+
 ### Failed to connect to the internal GitLab API
 
 If you see the following error: