Originally from this post.

I wrote a Thunderbird extension (and my first one too!) that allows the display of all available about: windows in Thunderbird. Shredder Alpha 3 and above is required though. It is called ViewAbout and can be downloaded from Mozilla Add-ons. (Firefox 3.0.x and above are supported from version 1.2, other applications are continuously added and [hopefully] supported.)

Enables access to various about: dialogs from the View menu. Every available and applicable about: dialog can be viewed, even those activated by other extensions.

about:, about:buildconfig, about:cache (and related), about:config, about:crashes, about:credits, about:license (generic Toolkit license), about:mozilla, about:neterror (seemingly useless), about:plugins, about:privatebrowsing, about:rights, about:robots, about:sessionrestore, about:weave.

These windows can be closed using Ctrl (or Cmd)-w. Note that some about: menu options may not show up in applications that do not support them.

Historical note: ViewAbout came about from a need to view about:crashes in Thunderbird, and it just expanded from there. ;-) 

I have also made ViewAbout’s AMO Dashboard public, so everyone can see just how many users need about:crashes or about:config and the like.

Development of ViewAbout has now shifted to Google Code.

Version changelog:

1.5: Support about:weave. Fix up ViewAbout’s JavaScript code to pass security validation. Re-enable about:neterror for those who love it for complete-ness’ sake. Add support up to Firefox 3.7a1pre.

1.4.2: Fixed up nit in 1.4.1.

1.4.1: Now supports Instantbird 0.2 and up. Thanks Nils Maier! Tidied up contributors section.

1.4: Now supports Firefox 2.0.0.x. Auto-detection for available about URLs in current application. Support for access keys in menu. Some code re-factorizations to reduce redundant code. Huge thanks go out to Dave Garrett for contributing this version.

1.3: Supports SeaMonkey 2.0a2 and above. Supports Sunbird 1.0pre and above. Added more about: pages – about:robots, about:sessionrestore, about:privatebrowsing, about:rights. Moved out doLoad and doUnLoad into a separate javascript file to reduce duplicate code.

1.2: Supports Firefox 3.0 and above. Supports Thunderbird 2.0 and above. (Note that some about: pages won’t show for Thunderbird 2.0.0.x because they’re based on an older Gecko 1.8.1.x branch)

1.1: Adds about:, about:cache, about:cache?device=disk, about:cache?device=memory and about:cache?device=offline. Removes Mac file metadata. Fixes error console error that pops up whenever an about: window is opened. Minor fixes.

1.0: Initial version.