All of the activities described in this chapter take place within the installed Plone site, not the management interface. In other words, you are limited to utilizing the tools that are part of the Plone application itself ”forms, tabs, links, and so forth. This includes helpful error messages when mistakes are made. For example, if you forget to complete a required field in a form, Plone returns an error message describing how to fix your error and continue with your desired action. Similarly, if you attempt to perform an action that is disallowed , such as attempting to undo an action that cannot be undone, Plone simply tells you that it can't be done ”it doesn't halt your program and send it spinning out of control.