Beyond Firefox's "about:config", a list of "about:" pages of major browsers.
By now most people have heard of the "about:config" page for editing preferences in Firefox. What most people don't know is there are quite a few other "about:" pages for Mozilla Firefox and Seamonkey as well as for the old Netscape, Internet Explorer, Opera, Flock, Konqueror, and Epiphany. All of these "about:" pages may be accessed by typing them into the location bar of the corresponding browser, just as you would any URL.
Here I will list the most common "about:" pages for each browser with an explanation of what they will display.
"about:" or "about:about" - Either of these, will give you version information concerning your build of Firefox.
"about:blank" - Displays a blank page.
"about:plugins" - Displays a page listing the names and information of allinstalled plugins.
"about:cache" - Displays cache service information.
"about:cache?device=memory" - Displays information about the memory usage, with each entry listed individually."about:cache?device=disk" - Same as above but displays the items cached to your disk along with cache location on disk and again the listing of cached items."about:mozilla" - Displays an amusing page from a fictional book titled "The Book of Mozilla"."about:buildconfig" - Displays the build target platform, build tools (compiler), and configure arguements."about:config" - Displays an interface for setting and adjusting a number of browser configuration components."about:credits" - Lists people who contributed to Mozilla."about:logo" - Seamonkey only. Shows about:screen logo."about:licence" - Displays the EULA."about:license" - Same as above."about:neterror" - Displays the default "page can not be reached" page.
"about:myworld" - Displays the Flock "Myworld" page.
"opera:blank" - Displays blank page."about:blank" - Same as above."opera:about" - Displays browser and configured path information."about:opera" - Same as above."opera:cache" - Displays cache content."opera:config" - For Opera 9.0 and newer only. Displays a configuration page allowing access to many configuration options not available through the preferences window."opera:drives" - Displays local drives of your system."opera:history" - Displays browser history."opera:plugins" - Displays installed browser plugins."opera:button" - Allows definition of a custom button for opera commands."opera:help" - Help directory shortcut.
(It should be noted that windows allows for the configuration of many of the about: pages in Explorer, therefore some pages may vary. These pages may be changed by the user, service packs or by ad/spyware.)"about:DesktopItemNavigationFailure" - Shows a navigation cancelled page."about:NavigationCanceled" - See above"about:NavigationFailure" - See above"about:Home" - Shows browsers current homepage."about:offlineinformation" - Displays page informing you that current page may not be viewed while offline."about:PostNotCached" - Displays warning that in order to refresh current page information from any forms will have to be re-entered."about:SecurityRisk" - Displays a page telling user it is unsafe to browse with current security settings.
"about:konqueror" - Displays a friendly start page.
(Epiphany uses the same layout engine as the Mozilla products. All Mozilla about: pages should work in Epiphany and have the same results. Below is the only Epiphany specific about: page.)"about:epiphany" - Displays a quote by Antoine de Saint-Exupry.
"about:people" - Used to redirect to Netscape's active employee listing."about:username" - Replace username with an active Netscape employee name from above to see that perrson's personal page."about:mozilla" - Same as in Firefox."about:language" - Replace "language" with a language such as "duetsche" to see Mozilla mascot in lederhosen. Other languages would get you the mascot in other traditional clothing."about:global" - Displays browser history.(Most of the Netscape about: pages were based on now defunct web addresses therefore they will no longer work, good luck)
Those are all of the "about:" pages I know of for the more popular browsers out there right now. I hope this list helps you, or at least entertains you for a few minutes. Enjoy.