When you create new Webs with FrontPage, their permissions are the same as those of the root Web by default.
Web have the same rights on the newly created Web.
Therefore, Add and Remove are unavailable, because the root permissions cannot be changed within a new Web. Unique permissions can be set so that a new Web does not inherit its permissions settings from the root Web. This allows a Web to be set with unique administrators, authors, and end users, even if you later make changes to the permissions of the root Web. Click the Settings tab, and then select the Use unique permissions for this web check box. Click Apply for the changes to take effect.