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.
Which element markers appear when you choose View > Invisible Elements depends 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.
You can create certain invisible elements (such as comments, named anchors, and scripts) using the buttons on the Invisibles panel in the Object palette. You can modify these elements using the Property inspector. See Object palette.