Fixed typo -- "a" user, not "an" user

docs/topics/auth/customizing.txt

@@ -276,7 +276,7 @@ can or cannot do with Task instances, specific to your application::
 
 The only thing this does is create those extra permissions when you run
 :djadmin:`manage.py migrate <migrate>`. Your code is in charge of checking the
-value of these permissions when an user is trying to access the functionality
+value of these permissions when a user is trying to access the functionality
 provided by the application (viewing tasks, changing the status of tasks,
 closing tasks.) Continuing the above example, the following checks if a user may
 view tasks::

docs/topics/auth/index.txt

@@ -12,7 +12,7 @@ User authentication in Django
 .. module:: django.contrib.auth
    :synopsis: Django's authentication framework.
 
-Django comes with an user authentication system. It handles user accounts,
+Django comes with a user authentication system. It handles user accounts,
 groups, permissions and cookie-based user sessions. This section of the
 documentation explains how the default implementation works out of the box, as
 well as how to :doc:`extend and customize </topics/auth/customizing>` it to