Much like Google Chrome about: pages, Firefox 4 there are also some hidden about: pages which shows information about memory usage, cached files, plug-ins, add-ons and more. Some Firefox 4 pages about: may confuse you, some pages are for diagnostic purposes only and some may be omitted because they require query strings, here is the complete list of Firefox 4 About: Pages.
1.about: Entering about: Firefox 4 address bar shows Firefox logo, version, links to pages with list of contributors, licensing information and build configuration, etc.
two.about: add-ons: Entering about:add-ons will open the Add-ons Manager.
3. about: buildconfig
4. about: cache
5 .about: configuration
6. about: accidents : This page will show bug reports sent by Mozilla’s bug reporter to Mozilla.
9. about: license
14.about: private browsing
19.about: sync log, about:sync-log1,about: sync guides pages shows information related to Firefox Sync which has synced your tabs and other information.
Finally, you can get a list of all these about: pages in Firefox 4 on a single page about what you’re with On.