update links

doc/user/project/pages/getting_started_part_one.md

@@ -62,7 +62,7 @@ which is highly recommendable and much faster than hardcoding.
 
 If you set up a GitLab Pages project on GitLab.com,
 it will automatically be accessible under a
-[subdomain of `namespace.pages.io`](https://docs.gitlab.com/ce/user/project/pages/).
+[subdomain of `namespace.pages.io`](introduction.md#gitlab-pages-on-gitlab-com).
 The `namespace` is defined by your username on GitLab.com,
 or the group name you created this project under.
 
@@ -73,6 +73,8 @@ Pages wildcard domain. This guide is valid for any GitLab instance,
 you just need to replace Pages wildcard domain on GitLab.com
 (`*.gitlab.io`) with your own.
 
+Learn more about [namespaces](../../group/index.html#namespaces).
+
 ### Practical examples
 
 #### Project Websites