Updated when signing in across spaces

Author: PhilReedData

TeSS_docs/accounts/user.md

@@ -7,7 +7,7 @@ If you want to register your materials, you can register for a user account.
 ```{admonition} Note for mutli-space TeSS instances
 :class: note
 If a TeSS instanace has multiple [spaces](../spaces/intro-spaces), please register one user account for all spaces. 
-For security reasons, you will need to log in to each space separately, even though you are using the same account.
+For security reasons, if the spaces are on different domains (`site1.com` and `site2.com`), you will need to log in to each space separately, even though you are using the same account.
 ```
 
 ## Register by email address