The member ID pattern is a regular expression against which member IDs are checked during the portal registration. It is necessary to limit the kinds of characters that can be used as a member ID because the ID can show up as part of a URL. Web URLs are restricted. Only change this setting if you really know what you are doing.

In order to use a pattern different from the shown default pattern simply fill in the text field and submit the form. To revert back to the default policy leave the text field empty.