Choose View > Invisible Elements to show or hide markers in the Document window that represent invisible elements such as forms, named anchors, comments, and scripts. Showing invisible elements lets you select and view them and change their properties in the Property inspector.
The element markers that appear when you choose View > Invisible Elements depend on the settings in the Invisible Elements panel of the Preferences dialog box. For example, you can specify that named anchors should be visible, but not line breaks. See Invisible Elements preferences.
Certain invisible elements (comments, named anchors, and scripts) can be created using the buttons on the Invisibles panel in the Object palette and modified with the Property inspector. See Object palette.