User names cannot contain spaces unless they are read-only (as in NT domain integration), and are limited to 64 characters in length.

Passwords can be neither blank, nor the number zero, and are limited to 30 characters in length. Set minimum password length on the Settings for all Users page (Server » Settings » User). See Setting user options.

Group names and group descriptions cannot begin with a space.

Channel locations (URLs) can contain only alphanumeric characters and characters used for their reserved purposes. Otherwise, they must be properly URL-encoded.