The PAGE INFO (Frame Info) Information Window is located under the INFORMATION button on the Accessibility Toolbar.
The Page Info (Frame Info) choice opens an Information Window with the tabs GENERAL, FORMS, LINKS, MEDIA. Select a tag to see the information for that area. The General tab lists information such as the URL, size, source, last date modifed, and meta information. The Forms, Links, and Media tabs list the items on the page that fall under these categories. Additional information about these items is also available from the Navigation dropdown menu.
Try this feature: Use the page http://cita.rehab.uiuc.edu/software/mozilla/test/ts-test-page-labels1.php to view the Page Information Window. Select the different tabs and note the information in the information panes.