about:bloat Displays BloatView output (disabled in release builds).
about:blocked Shows the malware protection page used when the
browser identifies a page as not safe for viewing. (Firefox 3-specific).
about:buildconfig Shows the arguments and options used to compile the build in use
about:cache Shows information about the Cache Service. Number of entries, location of cache, size of cache, etc. for both memory and disk cache.
about:cache?device=memory Shows individual entries in memory
about:cache?device=disk Shows individual entries on disk
about:cache?device=offline Shows individual entries for offline viewing. New to products based on Gecko 1.9 or later.
about:cache-entry Shows information about a cache entry. Used in
about:cache links Requires parameters.
about:config Shows an interface for viewing and setting a wide variety of configuration variables, many of which are not otherwise accessible
through the GUI (options panels)
about:crashes Shows details of crashes submitted by Mozilla's crash reporter (since Firefox 3).
about:credits Shows a list of all those who contributed to Mozilla
about:licence In the British English localised version, shows the content of
about:license but with all occurrences of license used as a noun replaced with licence (see American and British English spelling differences)
about:license Shows the Mozilla Public License (and the Netscape Public License) for the piece of software. (Only in products based on Gecko 1.8 or later)
about:logo Shows the logo used on the about: screen
about:mozilla easter egg: Shows a verse from The Book of Mozilla
about:neterror Shows the error page used when the browser could not access the requested path.
about:plugins Shows installed plug-ins.
about:robots Easter egg, beginning with March 8th, 2008 trunk builds.
about:rights Shows licensing information