Hi,
The default look of form elements is defined by forms.css in the “res” folder of your firefox installation. There are a few other css files there and the main one is called html.css which sets the default for most other elements.
This is forms.css:
/* ***** 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):
*
* 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 ***** */
/**
Styles for old GFX form widgets
**/
@namespace url(http://www.w3.org/1999/xhtml); /* set default namespace to HTML */
@namespace xul url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);
*|*::-moz-fieldset-content {
display: block;
height: 100%; /* Need this so percentage heights of kids work right */
}
/* miscellaneous form elements */
legend {
padding-left: 2px;
padding-right: 2px;
border: none;
position: static ! important;
float: none ! important;
width: -moz-fit-content ! important;
min-width: 0 ! important;
max-width: none ! important;
height: auto ! important;
min-height: 0 ! important;
max-height: none ! important;
white-space: nowrap;
}
fieldset {
display: block;
margin-left: 2px;
margin-right: 2px;
padding: 0.35em 0.625em 0.75em;
border: 2px groove ThreeDFace;
}
label {
cursor: default;
}
/* default inputs, text inputs, and selects */
/* Note: Values in nsNativeTheme IsWidgetStyled function
need to match textfield background/border values here */
input {
-moz-appearance: textfield;
/* The sum of border-top, border-bottom, padding-top, padding-bottom
must be the same here, for buttons, and for <select> (including its
internal padding magic) */
padding: 1px 0 1px 0;
border: 2px inset ThreeDFace;
background-color: -moz-Field;
color: -moz-FieldText;
font: -moz-field;
text-rendering: optimizeLegibility;
line-height: normal !important;
text-align: start;
text-transform: none;
word-spacing: normal;
letter-spacing: normal;
cursor: text;
-moz-binding: url("chrome://global/content/platformHTMLBindings.xml#inputFields");
text-indent: 0;
-moz-user-select: text;
text-shadow: none;
}
input > .anonymous-div {
white-space: pre;
word-wrap: normal !important;
}
textarea {
margin: 1px 0 1px 0;
border: 2px inset ThreeDFace;
background-color: -moz-Field;
color: -moz-FieldText;
font: medium -moz-fixed;
text-rendering: optimizeLegibility;
text-align: start;
text-transform: none;
word-spacing: normal;
letter-spacing: normal;
vertical-align: text-bottom;
cursor: text;
-moz-binding: url("chrome://global/content/platformHTMLBindings.xml#textAreas");
-moz-appearance: textfield-multiline;
text-indent: 0;
-moz-user-select: text;
text-shadow: none;
word-wrap: break-word;
}
textarea > scrollbar {
cursor: default;
}
textarea > .anonymous-div,
input > .anonymous-div {
overflow: auto;
border: 0px !important;
/* The 1px horizontal padding is for parity with Win/IE */
padding: 0px 1px;
margin: 0px;
/* XXXldb I'm not sure if we really want the 'text-decoration: inherit',
but it's needed to make 'text-decoration' "work" on text inputs. */
text-decoration: inherit;
ime-mode: inherit;
}
input:-moz-read-write,
textarea:-moz-read-write {
-moz-user-modify: read-write !important;
}
select {
margin: 0;
border-color: ThreeDFace;
background-color: -moz-Field;
color: -moz-FieldText;
font: -moz-list;
line-height: normal !important;
white-space: nowrap !important;
word-wrap: normal !important;
text-align: start;
cursor: default;
-moz-box-sizing: border-box;
-moz-user-select: none;
-moz-appearance: menulist;
border-width: 2px;
border-style: inset;
text-indent: 0;
overflow: -moz-hidden-unscrollable;
text-shadow: none;
}
/* Need the "select[size][multiple]" selector to override the settings on
'select[size="1"]', eg if one has <select size="1" multiple> */
select[size],
select[multiple],
select[size][multiple] {
/* Different alignment and padding for listbox vs combobox */
vertical-align: text-bottom;
padding: 1px 0 1px 0;
-moz-appearance: listbox;
}
select[size],
select[size="1"] {
/* Except this is not a listbox */
vertical-align: baseline;
padding: 0;
-moz-appearance: menulist;
}
select > input[type="button"] {
width: 12px;
height: 12px;
white-space: nowrap;
position: static !important;
background-image: url("arrow.gif") !important;
background-repeat: no-repeat !important;
background-position: center !important;
-moz-appearance: menulist-button;
/* Make sure to size correctly if the combobox has a non-auto height. */
height: 100% ! important;
-moz-box-sizing: border-box ! important;
/*
Make sure to align properly with the display frame. Note that we
want the baseline of the combobox to match the baseline of the
display frame, so the dropmarker is what gets the vertical-align.
*/
vertical-align: top !important;
}
select > input[type="button"]:active {
background-image: url("arrowd.gif") !important;
}
select:empty {
width: 2.5em;
}
*|*::-moz-display-comboboxcontrol-frame {
overflow: -moz-hidden-unscrollable;
/* This top/bottom padding plus the combobox top/bottom border need to
add up to the top/bottom borderpadding of text inputs and buttons */
padding-top: 1px;
padding-bottom: 1px;
-moz-padding-start: 4px;
-moz-padding-end: 0;
background-color: inherit;
color: inherit;
white-space: nowrap;
text-align: inherit;
-moz-user-select: none;
/* Make sure to size correctly if the combobox has a non-auto height. */
height: 100% ! important;
-moz-box-sizing: border-box ! important;
}
select::-moz-scrolled-content {
display: block !important;
}
option {
display: block;
float: none !important;
position: static !important;
min-height: 1em;
line-height: normal !important;
-moz-user-select: none;
text-indent: 0;
white-space: nowrap !important;
word-wrap: normal !important;
}
select > option {
padding-top : 0;
padding-bottom: 0;
-moz-padding-start: 3px;
-moz-padding-end: 5px;
}
option:checked {
background-color: -moz-html-cellhighlight !important;
color: -moz-html-cellhighlighttext !important;
}
select:focus > option:checked,
select:focus > optgroup > option:checked {
background-color: Highlight ! important;
color: HighlightText ! important;
}
optgroup {
display: block;
float: none !important;
position: static !important;
font: -moz-list;
line-height: normal !important;
font-style: italic;
font-weight: bold;
font-size: inherit;
-moz-user-select: none;
text-indent: 0;
white-space: nowrap !important;
word-wrap: normal !important;
}
optgroup > option {
-moz-padding-start: 20px;
font-style: normal;
font-weight: normal;
}
optgroup:before {
display: block;
content: attr(label);
}
*|*::-moz-dropdown-list {
z-index: 2147483647;
background-color: inherit;
-moz-user-select: none;
position: static !important;
float: none !important;
/*
* We can't change the padding here, because that would affect our
* intrinsic width, since we scroll. But at the same time, we want
* to make sure that our left border+padding matches the left
* border+padding of a combobox so that our scrollbar will line up
* with the dropmarker. So set our left border to 2px.
*/
border: 1px outset black !important;
border-left-width: 2px ! important;
}
input[disabled],
textarea[disabled],
option[disabled],
optgroup[disabled],
select[disabled] {
-moz-user-input: disabled;
-moz-user-focus: ignore;
color: GrayText;
background-color: ThreeDFace;
cursor: inherit;
}
option[disabled],
optgroup[disabled] {
background-color: transparent;
}
/* hidden inputs */
input[type="hidden"] {
-moz-appearance: none;
display: none;
padding: 0;
border: 0;
cursor: auto;
-moz-user-focus: ignore;
-moz-binding: none;
}
/* image buttons */
input[type="image"] {
-moz-appearance: none;
padding: 0;
border: none;
background-color: transparent;
font-family: sans-serif;
font-size: small;
cursor: pointer;
-moz-binding: none;
}
input[type="image"][disabled] {
cursor: inherit;
}
input[type="image"]:focus {
/* Don't specify the outline-color, we should always use initial value. */
outline: 1px dotted;
}
/* file selector */
input[type="file"] {
-moz-appearance: none;
white-space: nowrap;
cursor: default;
-moz-binding: none;
padding: 0 !important;
border-style: none !important;
}
input[type="file"] > input[type="text"] {
border-color: inherit;
background-color: inherit;
color: inherit;
font-size: inherit;
letter-spacing: inherit;
}
/* button part of file selector */
input[type="file"] > input[type="button"] {
height: inherit;
font-size: inherit;
letter-spacing: inherit;
}
/* radio buttons */
input[type="radio"] {
-moz-appearance: radio;
margin: 3px 3px 0px 5px;
-moz-border-radius: 100% !important;
}
/* check boxes */
input[type="checkbox"] {
-moz-appearance: checkbox;
margin: 3px 3px 3px 4px;
-moz-border-radius: 0 !important;
}
/* common features of radio buttons and check boxes */
/* NOTE: The width, height, border-width, and padding here must all
add up the way nsFormControlFrame::GetIntrinsic(Width|Height)
expects them to, or they will not come out with total width equal
to total height on sites that set their 'width' or 'height' to 'auto'.
(Should we maybe set !important on width and height, then?) */
input[type="radio"],
input[type="checkbox"] {
-moz-box-sizing: border-box;
width: 13px;
height: 13px;
cursor: default;
padding: 0 !important;
-moz-binding: none;
/* same colors as |input| rule, but |!important| this time. */
background-color: -moz-Field ! important;
color: -moz-FieldText ! important;
border: 2px inset ThreeDFace ! important;
}
input[type="radio"][disabled],
input[type="radio"][disabled]:active,
input[type="radio"][disabled]:hover,
input[type="radio"][disabled]:hover:active,
input[type="checkbox"][disabled],
input[type="checkbox"][disabled]:active,
input[type="checkbox"][disabled]:hover,
input[type="checkbox"][disabled]:hover:active {
padding: 1px;
border: 1px inset ThreeDShadow ! important;
/* same as above, but !important */
color: GrayText ! important;
background-color: ThreeDFace ! important;
cursor: inherit;
}
input[type="checkbox"]:focus,
input[type="radio"]:focus {
border-style: groove !important;
}
input[type="checkbox"]:hover:active,
input[type="radio"]:hover:active {
background-color: ThreeDFace ! important;
border-style: inset !important;
}
/* buttons */
/* Note: Values in nsNativeTheme IsWidgetStyled function
need to match button background/border values here */
button,
input[type="reset"],
input[type="button"],
input[type="submit"] {
-moz-appearance: button;
/* The sum of border-top, border-bottom, padding-top, padding-bottom
must be the same here, for text inputs, and for <select>. For
buttons, make sure to include the -moz-focus-inner border/padding. */
padding: 0px 6px 0px 6px;
border: 2px outset ButtonFace;
background-color: ButtonFace;
color: ButtonText;
font: -moz-button;
line-height: normal !important;
white-space: pre;
cursor: default;
-moz-box-sizing: border-box;
-moz-user-select: none;
-moz-binding: none;
text-align: center;
text-shadow: none;
}
button {
/* Buttons should lay out like "normal" html, mostly */
white-space: inherit;
text-indent: 0;
}
*|*::-moz-button-content {
display: block;
}
button:hover,
input[type="reset"]:hover,
input[type="button"]:hover,
input[type="submit"]:hover {
background-color: -moz-buttonhoverface;
color: -moz-buttonhovertext;
}
button:active:hover,
input[type="reset"]:active:hover,
input[type="button"]:active:hover,
input[type="submit"]:active:hover {
padding: 0px 5px 0px 7px;
border-style: inset;
background-color: ButtonFace;
color: ButtonText;
}
button::-moz-focus-inner,
input[type="reset"]::-moz-focus-inner,
input[type="button"]::-moz-focus-inner,
input[type="submit"]::-moz-focus-inner,
input[type="file"] > input[type="button"]::-moz-focus-inner {
padding: 0px 2px 0px 2px;
border: 1px dotted transparent;
}
button:focus::-moz-focus-inner,
input[type="reset"]:focus::-moz-focus-inner,
input[type="button"]:focus::-moz-focus-inner,
input[type="submit"]:focus::-moz-focus-inner,
input[type="file"] > input[type="button"]:focus::-moz-focus-inner {
border-color: ButtonText;
}
button[disabled]:active, button[disabled],
input[type="reset"][disabled]:active,
input[type="reset"][disabled],
input[type="button"][disabled]:active,
input[type="button"][disabled],
select[disabled] > input[type="button"],
select[disabled] > input[type="button"]:active,
input[type="submit"][disabled]:active,
input[type="submit"][disabled] {
/* The sum of border-top, border-bottom, padding-top, padding-bottom
must be the same here and for text inputs */
padding: 0px 6px 0px 6px;
border: 2px outset ButtonFace;
color: GrayText;
cursor: inherit;
}
/*
* Make form controls inherit 'unicode-bidi' transparently as required by
* their various anonymous descendants and pseudo-elements:
*
* <textarea> and <input type="text">:
* inherit into the XULScroll frame with class 'anonymous-div' which is a
* child of the text control.
*
* Buttons (either <button>, <input type="submit">, <input type="button">
* or <input type="reset">)
* inherit into the ':-moz-button-content' pseudo-element.
*
* <select>:
* inherit into the ':-moz-display-comboboxcontrol-frame' pseudo-element and
* the <optgroup>'s ':before' pseudo-element, which is where the label of
* the <optgroup> gets displayed. The <option>s don't use anonymous boxes,
* so they need no special rules.
*/
textarea > .anonymous-div,
input > .anonymous-div,
*|*::-moz-button-content,
*|*::-moz-display-comboboxcontrol-frame,
optgroup:before {
unicode-bidi: inherit;
}
/*
* Force the text control child of file input controls to have left-to-right
* directionality. Otherwise filenames containing right-to-left characters
* will be reordered with chaotic results.
*/
input[type="file"] > input[type="text"] {
direction: ltr !important;
text-align: inherit;
}
@media print {
input, textarea, select, button {
-moz-user-input: none !important;
}
input[type="file"] { height: 2em; }
}
In reality you don’t really need to know anything about it as it uses proprietary styles to style elements in most cases. It will be called before any of the author stylesheets and so your code will over-ride the default settings where you are allowed to.
Remember that not all form elements can be styled fully and some not at all.
All browsers have default system styles applied otherwise you would see a jumbled mess of code in your page including html from the head elements.
