nag wrote: Thanks for the Primer Book, that's the manual I missed, especially for the tabs positions (and some other points).

I didn't find how to turn off Joomla emails to new users (I found how to turn off Joomla emails to administrator when somebody subscribes.) So I didn't change this setting.

When I turn off Joomla registrations, the bug is unfortunately the same.

The CB Primer Book also references the getting started articles as does every cb install message.

www.joomlapolis.com/documentation/community-builder/getting-started

you can see how to disable joomla emails here.

Your 404 issue needs more debuging - what is the original URL you are trying to access when you get this bad page?