Turning off site/group registrations
By default your web site will allow users to register for an account to login to your web site. If their application is approved they'll be able to login and also apply for membership of specific areas of the web site.
Giving users login access allows them to update their contact information, set their mailing preferences and allows you to display information privately to them, or give only them access to view/comment in a particular discussion forum.
Sometimes you may wish to stop users registering for an account i.e. hide the "Register" option, or stop them from applying to a particular group. You can do this as follows:
Select the group that you wish to restrict membership registrations for. If you wish to stop registrations for the whole site then it would be your root group, if it's applications to a particular group then you'd select the appropriate user group folder. Note: Only user groups allow membership applications.
Click on the Group Settings icon on the top right of the page, the group settings will be displayed shortly afterwards.
Select the Access tab.
Under Applications select the drop down to show 'No-one' and this will prevent anyone registering to this group.