about:kitchensink is the result of a bug fix (Bugzilla Bug 122411, which you can read about in detail at http://bugzilla.mozilla.org/show_bug.cgi?id=122411), in which the goal was to demonstrate a use of the XHTML 1.1 standard in Mozilla. The feature will be included in all future versions of Mozilla for the foreseeable future.
In other words, about:kitchensink is an Easter egg with some degree of usefulness found in Mozilla.
For those of you using a recent build of Mozilla as your web browser and if you're not, why aren't you? Run, don't walk, to http://www.mozilla.org and get one!, try typing about:kitchensink into the location bar of your browser. For those of you who don't own Mozilla and would like to see what is going on, look at:
Recent standard compliant browsers will see the phrase "And the kitchen sink, too..." followed by a large ASCII art of a kitchen sink. The handle on the sink will automatically turn on and off a couple of times, then stay on. At this point, you can click on the ASCII art and cause the water to turn on and off.
I don't see anything! or I get errors!
This is largely because the above widget utilizes a great deal of very recent web authoring standards. If you view this with Internet Explorer 6, the issue is related to some errors in IE's implementation of the XHTML 1.1 standard.
FYI, Internet Explorer 6 throws the following error when visiting the kitchen sink:
The XML page cannot be displayed
Cannot view XML input using style sheet. Please correct the error and then click the Refresh button, or try again later.
Parameter entity must be defined before it is used. Error processing resource
'http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd'. Line 85, Position 2
Doesn't this bloat up Mozilla, making it a gigantic Microsoft Excel 97-esque piece of bloatware?
It adds about a hundred bytes to a file that is not actually part of the Mozilla binary, which just points to the URL described above. The actual "kitchen sink" is located on the mozilla.org website.
Well, that was "useful." What's the point?
The purpose of about:kitchensink is twofold:
1. To demonstrate the fact that Mozilla is now fully compliant with XHTML 1.1.
The "kitchen sink" demo was created originally for the purpose of verifying XHTML 1.1 compliance, as it is a relatively simple tool that does a thorough test of many of the specifications of the XHTML 1.1 standard.
In the future, it will be used to continue to test the XHTML 1.1 standard compliance in later versions of the Mozilla web browser.
2. To assert Mozilla's completeness and dominance.
In terms of standards compliance and web surfing features, Mozilla is pretty much the most complete web browser available. It displays virtually everything you can throw at it well (without the errors that IE 6 throws, as seen above, nor the complete "barfing" that earlier browsers throw), especially code that is standards-compliant.
Isn't this stuff taking away from development time for Mozilla developers?
The "feature" was developed by a couple of volunteer programmers who don't invest a lot of time into the project. Instead, their goal was to make a good XHTML 1.1 tester and they achieved their goal while having a little bit of fun with it. One shouldn't lose sight of the fact that most of Mozilla's development staff are volunteers (myself included), so we occasionally try to have some fun in situations where it doesn't bog down the project.
about:kitchensink - it's all about flipping a nozzle on an ASCII version of a kitchen sink.