gecko-dev/servo/resources/servo.css

button,
input {
  background: white;
  min-height: 1.0em;
  padding: 0em;
  padding-left: 0.25em;
  padding-right: 0.25em;
  border: solid lightgrey 1px;
  color: black;
  font-family: sans-serif;
  font-size: 0.8333em;
  text-align: left;
  line-height: 1.8;
}

textarea {
  background: white;
  min-height: 1.0em;
  padding: 0em;
  padding-left: 0.25em;
  padding-right: 0.25em;
  border: solid lightgrey 1px;
  color: black;
  font-family: sans-serif;
  font-size: 0.8333em;
  white-space: pre-wrap;
}

input::selection,
textarea::selection {
  background: rgba(176, 214, 255, 1.0);
  color: black;
}

button,
input[type="button"],
input[type="submit"],
input[type="reset"] {
  background: lightgrey;
  border-top: solid 1px #EEEEEE;
  border-left: solid 1px #CCCCCC;
  border-right: solid 1px #999999;
  border-bottom: solid 1px #999999;
  text-align: center;
  color: black;
}

input[type="hidden"] { display: none !important }

input[type="checkbox"],
input[type="radio"] {
  font-family: monospace !important;
  border: none !important;
  background: transparent;
}

input[type="checkbox"]::before {
  display: inline-block;
  border: solid currentcolor 1px;
  content: "";
  padding: 0;
  width: 1em;
  height: 1em;
  text-align: center;
}

input[type="checkbox"]:checked::before { content: "✓"; }
input[type="checkbox"]:indeterminate::before { content: "-"; }

input[type="radio"]::before {
  display: inline-block;
  border: solid currentcolor 1px;
  content: "";
  padding: 0;
  width: 1em;
  height: 1em;
  border-radius: 50%;
  text-align: center;
}

input[type="radio"]:checked::before { content: "●"; line-height: 1em; }

input[type="file"]::before {
  content: "Choose File";
}

input[type="file"] {
  background: lightgrey;
  text-align: center;
  vertical-align: middle;
  color: black;
}

select {
  border-style: solid;
  border-width: 1px;
  background: white;
}

select[multiple]              { padding: 0em 0.25em; }
select:not([multiple])        { padding: 0.25em 0.5em; border-radius: 6px; }

select:not([multiple])::after {
  content: "";
  display: inline-block;
  border-width: 5.2px 3px 0 3px;
  border-style: solid;
  border-color: currentcolor transparent transparent transparent;
  margin-left: 0.5em;
}

select:not([multiple]) option           { display: none !important; }
select:not([multiple]) option[selected] { display: inline !important; }
select[multiple] option                 { display: block !important; }
select[multiple] option[selected]       { background-color: grey; color: white; }
select[multiple]:focus option[selected] { background-color: darkblue; }

td[align="left"]    { text-align: left; }
td[align="center"]  { text-align: center; }
td[align="right"]   { text-align: right; }

center { text-align: -servo-center; }

label { cursor: default; }

input:not([type=radio i]):not([type=checkbox i]):not([type=reset i]):not([type=button i]):not([type=submit i]),
textarea {
  cursor: text;
  overflow: hidden;
  -servo-overflow-clip-box: content-box;
}

input:not([type=radio i]):not([type=checkbox i]):not([type=reset i]):not([type=button i]):not([type=submit i]) {
  white-space: pre;
}

textarea {
  overflow: auto;
}

/* https://html.spec.whatwg.org/multipage/rendering.html#the-details-and-summary-elements */
details {
  display: block;
}

details::-servo-details-summary {
  margin-left: 40px;
  display: list-item;
  list-style: disclosure-closed;
}

details[open]::-servo-details-summary {
  list-style: disclosure-open;
}

*|*::-servo-details-content {
  margin-left: 40px;
  overflow: hidden;
  display: block;
}

/*
 * Until servo supports svg properly, make sure to at least prevent svg
 * children from being layed out and rendered like usual html.
 * https://github.com/servo/servo/issues/10646
 */
svg > * {
  display: none;
}

/* style for text node. */
*|*::-servo-text {
    margin: 0;
    text-overflow: inherit;
    overflow: inherit;
}

/* style for text in input elements. */
*|*::-servo-input-text {
    margin: 0;
}

*|*::-servo-table-wrapper {
    display: table;
    border: none;
}

*|*::-servo-anonymous-table-wrapper {
    position: static;
    margin: 0;
    counter-increment: none;
}

*|*::-servo-anonymous-table {
    display: table;
    position: static;
    border: none;
    padding: 0;
    counter-increment: none;
}

*|*::-servo-anonymous-table-row {
    display: table-row;
    position: static;
    border: none;
    counter-increment: none;
}

*|*::-servo-anonymous-table-cell {
    display: table-cell;
    position: static;
    border: none;
    counter-increment: none;
}

*|*::-servo-anonymous-block {
    display: block;
    position: static;
    border: none;
    padding: 0;
    margin: 0;
    width: auto;
    height: auto;
}

/* The outer fragment wrapper of an inline-block. */
*|*::-servo-inline-block-wrapper {
    position: static;
    border: none;
    padding: 0;
    margin: 0;
}

/* The outer fragment wrapper of an inline absolute hypothetical fragment. */
*|*::-servo-inline-absolute {
    clip: auto;
    border: none;
    padding: 0;
    margin: 0;
}