Plone 3 uses viewlets to manage various standard page elements, such the logo, the navigation breadcrumbs, and the personal bar. Viewlets are registered to a viewlet manager, which controls which viewlets are displayed, and in which order they are rendered.
To see which viewlet managers and viewlets are used to compose a page, append
/@@manage-viewlets to a URL.
Note that this only works with viewlet managers based on the
plone.app.viewletmanager package. All of Plone’s viewlet managers use this, but third-party products may come with ...