Firefox 3’s Internal Rendering CSS

I was poking around Firefox's file and folder structure today. I've been doing research on how each browser vendor chooses to render CSS and, more specifically, what their default CSS stylesheet looks like. After a few minutes, I found a html.css file in the C:\Program Files\Mozilla Firefox\res directory.

Firefox 3's Default Stylesheet

/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Blake Ross <BlakeR1234@aol.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

@namespace url(http://www.w3.org/1999/xhtml); /* set default namespace to HTML */

/* bidi */

[dir="rtl"] {
  direction: rtl;
  unicode-bidi: embed;
}
[dir="ltr"] {
  direction: ltr;
  unicode-bidi: embed;
}
bdo[dir] {
  unicode-bidi: bidi-override;
}

/* blocks */

html, div, map, dt, isindex, form {
  display: block;
}

body {
  display: block;
  margin: 8px;
}

p, dl, multicol {
  display: block;
  margin: 1em 0;
}

dd {
  display: block;
  -moz-margin-start: 40px;
}

blockquote {
  display: block;
  margin: 1em 40px;
}

address {
  display: block;
  font-style: italic;
}

center {
  display: block;
  text-align: -moz-center;
}

blockquote[type=cite] {
  display: block;
  margin: 1em 0px;
  -moz-padding-start: 1em;
  -moz-border-start: solid;
  border-color: blue;
  border-width: thin;
}

span[_moz_quote=true] {
  color: blue;
}

pre[_moz_quote=true] {
  color: blue;
}

h1 {
  display: block;
  font-size: 2em;
  font-weight: bold;
  margin: .67em 0;
}

h2 {
  display: block;
  font-size: 1.5em;
  font-weight: bold;
  margin: .83em 0;
}

h3 {
  display: block;
  font-size: 1.17em;
  font-weight: bold;
  margin: 1em 0;
}

h4 {
  display: block;
  font-weight: bold;
  margin: 1.33em 0;
}

h5 {
  display: block;
  font-size: 0.83em;
  font-weight: bold;
  margin: 1.67em 0;
}

h6 {
  display: block;
  font-size: 0.67em;
  font-weight: bold;
  margin: 2.33em 0;
}

listing {
  display: block;
  font-family: -moz-fixed;
  font-size: medium;
  white-space: pre;
  margin: 1em 0;
}

xmp, pre, plaintext {
  display: block;
  font-family: -moz-fixed;
  white-space: pre;
  margin: 1em 0;
}

/* tables */

table {
  display: table;
  border-spacing: 2px;
  border-collapse: separate;
  margin-top: 0;
  margin-bottom: 0;
  /* XXXldb do we want this if we're border-collapse:collapse ? */
  -moz-box-sizing: border-box;
  text-indent: 0;
}

table[align="left"] {
  float: left;
}

table[align="right"] {
  float: right;
  text-align: start;
}

table[rules]:not([rules="none"]) {
  border-collapse: collapse;
}
   
/* caption inherits from table not table-outer */  
caption {
  display: table-caption;
  text-align: center;
  -moz-box-sizing: border-box;
}

table[align="center"] > caption {
  margin-left: auto;
  margin-right: auto;
}

table[align="center"] > caption[align="left"] {
  margin-right: 0;
}

table[align="center"] > caption[align="right"] {
  margin-left: 0;
}

tr {
  display: table-row;
  vertical-align: inherit;
}

col {
  display: table-column;
}

colgroup {
  display: table-column-group;
}

tbody {
  display: table-row-group;
  vertical-align: middle;
}

thead {
  display: table-header-group;
  vertical-align: middle;
}

tfoot {
  display: table-footer-group;
  vertical-align: middle;
}

/* for XHTML tables without tbody */
table > tr {
  vertical-align: middle;
}

td { 
  display: table-cell;
  vertical-align: inherit;
  text-align: inherit; 
  padding: 1px;
}

th {
  display: table-cell;
  vertical-align: inherit;
  font-weight: bold;
  padding: 1px;
}

tr > form:-moz-is-html, tbody > form:-moz-is-html,
thead > form:-moz-is-html, tfoot > form:-moz-is-html,
table > form:-moz-is-html {
  /* Important: don't show these forms in HTML */
  display: none !important;
}

/* inlines */

q:before {
  content: open-quote;
}

q:after {
  content: close-quote;
}

b, strong {
  font-weight: bolder;
}

i, cite, em, var, dfn {
  font-style: italic;
}

tt, code, kbd, samp {
  font-family: -moz-fixed;
}

u, ins {
  text-decoration: underline;
}

s, strike, del {
  text-decoration: line-through;
}

blink {
  text-decoration: blink;
}

big {
  font-size: larger;
}

small {
  font-size: smaller;
}

sub {
  vertical-align: sub;
  font-size: smaller;
  line-height: normal;
}

sup {
  vertical-align: super;
  font-size: smaller;
  line-height: normal;
}

nobr {
  white-space: nowrap;
}

/* titles */
abbr[title], acronym[title] {
  border-bottom: dotted 1px;
}

/* lists */

ul, menu, dir {
  display: block;
  list-style-type: disc;
  margin: 1em 0;
  -moz-padding-start: 40px;
}

ol {
  display: block;
  list-style-type: decimal;
  margin: 1em 0;
  -moz-padding-start: 40px;
}

li {
  display: list-item;
}

/* nested lists have no top/bottom margins */
ul ul,   ul ol,   ul dir,   ul menu,   ul dl,
ol ul,   ol ol,   ol dir,   ol menu,   ol dl,
dir ul,  dir ol,  dir dir,  dir menu,  dir dl,
menu ul, menu ol, menu dir, menu menu, menu dl,
dl ul,   dl ol,   dl dir,   dl menu,   dl dl {
  margin-top: 0;
  margin-bottom: 0;
}

/* 2 deep unordered lists use a circle */
ol ul,   ul ul,   menu ul,   dir ul,
ol menu, ul menu, menu menu, dir menu,
ol dir,  ul dir,  menu dir,  dir dir {
  list-style-type: circle;
}

/* 3 deep (or more) unordered lists use a square */
ol ol ul,     ol ul ul,     ol menu ul,     ol dir ul,
ol ol menu,   ol ul menu,   ol menu menu,   ol dir menu,
ol ol dir,    ol ul dir,    ol menu dir,    ol dir dir,
ul ol ul,     ul ul ul,     ul menu ul,     ul dir ul,
ul ol menu,   ul ul menu,   ul menu menu,   ul dir menu,
ul ol dir,    ul ul dir,    ul menu dir,    ul dir dir,
menu ol ul,   menu ul ul,   menu menu ul,   menu dir ul,
menu ol menu, menu ul menu, menu menu menu, menu dir menu,
menu ol dir,  menu ul dir,  menu menu dir,  menu dir dir,
dir ol ul,    dir ul ul,    dir menu ul,    dir dir ul,
dir ol menu,  dir ul menu,  dir menu menu,  dir dir menu,
dir ol dir,   dir ul dir,   dir menu dir,   dir dir dir {
  list-style-type: square;
}


/* leafs */

/* <hr> noshade and color attributes are handled completely by
 * the nsHTMLHRElement attribute mapping code
 */
hr {
  display: block;
  height: 2px;
  border: 1px inset;
  margin: 0.5em auto 0.5em auto;
  color: gray;
  -moz-float-edge: margin-box;
  -moz-box-sizing: border-box;
}

hr[size="1"] {
  border-style: solid none none none;
}

*|*:-moz-any-link img, img[usemap], object[usemap] {
  border: 2px solid;
}

img:-moz-broken::before, input:-moz-broken::before,
img:-moz-user-disabled::before, input:-moz-user-disabled::before,
img:-moz-loading::before, input:-moz-loading::before,
applet:-moz-empty-except-children-with-localname(param):-moz-broken::before,
applet:-moz-empty-except-children-with-localname(param):-moz-user-disabled::before {
  content: -moz-alt-content !important;
  unicode-bidi: embed;
}

object:-moz-broken > *|*, applet:-moz-broken > *|*
object:-moz-user-disabled > *|*, applet:-moz-user-disabled > *|* {
  /*
    Inherit in the object's alignment so that if we aren't aligned explicitly
    we'll end up in the right place vertically.  See bug 36997.  Note that this
    is not !important because we _might_ be aligned explicitly.
  */
  vertical-align: inherit;
}

img:-moz-suppressed, input:-moz-suppressed, object:-moz-suppressed,
embed:-moz-suppressed, applet:-moz-suppressed {
  /*
    Set visibility too in case the page changes display.  Note that we _may_
    want to just set visibility and not display, in general, if we find that
    display:none breaks too many layouts.  And if we decide we really do want
    people to be able to right-click blocked images, etc, we need to set
    neither one, and hack the painting code.... :(
   */
  display: none !important;
  visibility: hidden !important;
}

img[usemap], object[usemap] {
  color: blue;
}

frameset {
  display: block ! important;
  overflow: -moz-hidden-unscrollable;
  position: static ! important;
  float: none ! important;
  border: none ! important;
}

frame {
  border: none ! important;
}

iframe {
  border: 2px inset;
}

noframes {
  display: none;
}

spacer {
  position: static ! important;
  float: none ! important;
}

canvas {
  -moz-user-select: none;
}

/* focusable content: anything w/ tabindex >=0 is focusable */
abbr:focus, acronym:focus, address:focus, applet:focus, b:focus, 
base:focus, big:focus, blockquote:focus, br:focus, canvas:focus, caption:focus,
center:focus, cite:focus, code:focus, col:focus, colgroup:focus, dd:focus,
del:focus, dfn:focus, dir:focus, div:focus, dl:focus, dt:focus, em:focus,
fieldset:focus, font:focus, form:focus, h1:focus, h2:focus, h3:focus, h4:focus,
h5:focus, h6:focus, hr:focus, i:focus, img:focus, ins:focus, 
kbd:focus, label:focus, legend:focus, li:focus, link:focus, menu:focus, 
object:focus, ol:focus, p:focus, pre:focus, q:focus, s:focus, samp:focus, 
small:focus, span:focus, strike:focus, strong:focus, sub:focus, sup:focus, 
table:focus, tbody:focus, td:focus, tfoot:focus, th:focus, thead:focus, 
tr:focus, tt:focus, u:focus, ul:focus, var:focus {
  /* Don't specify the outline-color, we should always use initial value. */
   outline: 1px dotted;
}

/* hidden elements */
area, base, basefont, head, meta, script, style, title,
noembed, param {
   display: none;
}

/* emulation of non-standard HTML <marquee> tag */
marquee {
  width: -moz-available;
  display: inline-block;
  vertical-align: text-bottom;
  text-align: start;
  -moz-binding: url('chrome://xbl-marquee/content/xbl-marquee.xml#marquee-horizontal');
}

marquee[direction="up"], marquee[direction="down"] {
  -moz-binding: url('chrome://xbl-marquee/content/xbl-marquee.xml#marquee-vertical');
  height: 200px;
}

/* PRINT ONLY rules follow */
@media print {

  marquee { -moz-binding: none; }

  /* XXX this should not be necessary, we should be stopping blinking
     of any kind in print preview, not just the <blink> element */
  blink {
    text-decoration: none;
  }
 
}

Firefox's default stylesheet is an 11kb beast. How would you change the stylesheet? Does Firefox cause any reset.css hell for you? Have you hacked your Firefox default stylesheet? Share your thoughts.