normalize.css v3.0.1解读

normalize-V3.0.1.css

/*! normalize.css v3.0.1 | MIT License | git.io/normalize */

/**
 * 1. Set default font family to sans-serif.
 * 2. Prevent iOS text size adjust after orientation change, without disabling
 *    user zoom.
 * 1. 设置默认的字体sans-serif.
 * 2. 当屏幕方向改变的时候, 阻止ios自动调整文本大小. 
 * https://developer.mozilla.org/en-US/docs/Web/CSS/text-size-adjust
 */

html {
  font-family: sans-serif; /* 1 */
  -ms-text-size-adjust: 100%; /* 2 */
  -webkit-text-size-adjust: 100%; /* 2 */
}

/**
 * Remove default margin.
 * 删除默认的margin
 */

body {
  margin: 0;
}

/* HTML5 display definitions
   HTML5元素关于display属性的定义
   ========================================================================== */

/**
 * Correct `block` display not defined for any HTML5 element in IE 8/9.
 * 下面未在IE8/9中定义display属性的任意HTML5元素修正为`block`
 * Correct `block` display not defined for `details` or `summary` in IE 10/11 and Firefox.
 * 未在IE10/11和FireFox定义display属性的元素`details`或`summary`,修正为`block` 
 * Correct `block` display not defined for `main` in IE 11.
 * 未在IE11中定义display属性的`main`元素,修正为`block`
 */

article,
aside,
details,
figcaption,
figure,
footer,
header,
hgroup,
main,
nav,
section,
summary {
  display: block;
}

/**
 * 1. Correct `inline-block` display not defined in IE 8/9.
 * 1. 下面在IE8/9中未定义display属性,修正为`inline-block`
 * 2. Normalize vertical alignment of `progress` in Chrome, Firefox, and Opera.
 * 2. 在Chrome, FireFox和Opera，让progress垂直对齐
 */

audio,
canvas,
progress,
video {
  display: inline-block; /* 1 */
  vertical-align: baseline; /* 2 */
}

/**
 * Prevent modern browsers from displaying `audio` without controls.
 * 阻止现代浏览器显示audio在未定义controls属性的情况下(在chrome35,FireFox30和IE10没有发现这个问题)
 * http://www.w3schools.com/tags/tag_audio.asp
 * Remove excess height in iOS 5 devices.
 * 在IOS 5设备中,去除元素audio中显示多余的高度
 */

audio:not([controls]) {
  display: none;
  height: 0;
}

/**
 * Address `[hidden]` styling not present in IE 8/9/10.
 * 用样式去实现在IE 8/9/10中不支持的hidden属性
 * http://www.w3schools.com/tags/att_global_hidden.asp
 * Hide the `template` element in IE 8/9/11, Safari, and Firefox < 22.
 * 在IE 8/9/11, Safari, and Firefox < 22 隐藏template元素
 */

[hidden],
template {
  display: none;
}

/* Links
   ========================================================================== */

/**
 * Remove the gray background color from active links in IE 10.
 * 删除IE10中active link的灰色背景色
 */

a {
  background: transparent;
}

/**
 * Improve readability when focused and also mouse hovered in all browsers.
 * 清除a标签在hover和active时的outline
 */

a:active,
a:hover {
  outline: 0;
}

/* Text-level semantics
   ========================================================================== */

/**
 * Address styling not present in IE 8/9/10/11, Safari, and Chrome.
 * 处理在IE 8/9/10/11, Safari, and Chrome中的title无下划点线的问题，为与FireFox一致
 * http://www.w3schools.com/tags/tag_audio.asp
 */

abbr[title] {
  border-bottom: 1px dotted;
}

/**
 * Address style set to `bolder` in Firefox 4+, Safari, and Chrome.
 * 在Firefox 4+, Safari, and Chrome默认字体样式是加粗，修正所有浏览器与它们一致
 */

b,
strong {
  font-weight: bold;
}

/**
 * Address styling not present in Safari and Chrome.
 * 在Safari and Chrome处理dfn标签样式不存在的情况(chrome30下测试是OK的)
 * http://www.w3schools.com/tags/tag_dfn.asp
 */

dfn {
  font-style: italic;
}

/**
 * Address variable `h1` font-size and margin within `section` and `article`
 * contexts in Firefox 4+, Safari, and Chrome.
 * 处理h1标签在section和article中的字体大小和margin
 */

h1 {
  font-size: 2em;
  margin: 0.67em 0;
}

/**
 * Address styling not present in IE 8/9.
 * 在IE8/9中用样式处理mark标签的样式(IE9测试是支持mark标签，样式和其他浏览器也一致)
 * http://www.w3schools.com/tags/tryit.asp?filename=tryhtml5_mark
 */

mark {
  background: #ff0;
  color: #000;
}

/**
 * Address inconsistent and variable font size in all browsers.
 * 处理small标签的样式,让其字体大小在所有浏览器一致
 */

small {
  font-size: 80%;
}

/**
 * Prevent `sub` and `sup` affecting `line-height` in all browsers.
 * 阻止`sub` and `sup` 影响行高在所有的浏览器
 */

sub,
sup {
  font-size: 75%;
  line-height: 0;
  position: relative;
  vertical-align: baseline;
}

sup {
  top: -0.5em;
}

sub {
  bottom: -0.25em;
}

/* Embedded content
   ========================================================================== */

/**
 * Remove border when inside `a` element in IE 8/9/10.
 * 当a标签在img元素的时候,去除它的边框
 */

img {
  border: 0;
}

/**
 * Correct overflow not hidden in IE 9/10/11.
 * 修在overflow在IE9/10/11中不隐藏
 */

svg:not(:root) {
  overflow: hidden;
}

/* Grouping content
   ========================================================================== */

/**
 * Address margin not present in IE 8/9 and Safari.
 * 修正figure标签在IE8/9和Safari中没有margin
 */

figure {
  margin: 1em 40px;
}

/**
 * Address differences between Firefox and other browsers.
 * 修正hr标签在FireFox和其他浏览器的不同
 */

hr {
  -moz-box-sizing: content-box;
  box-sizing: content-box;
  height: 0;
}

/**
 * Contain overflow in all browsers.
 * 在所有浏览器中包含overflow
 */

pre {
  overflow: auto;
}

/**
 * Address odd `em`-unit font size rendering in all browsers.
 * 不清楚为什么这样处理
 */

code,
kbd,
pre,
samp {
  font-family: monospace, monospace;
  font-size: 1em;
}

/* Forms
   ========================================================================== */

/**
 * Known limitation: by default, Chrome and Safari on OS X allow very limited
 * styling of `select`, unless a `border` property is set.
 */

/**
 * 1. Correct color not being inherited.
 * 1. 修正color属性不能被继承
 *    Known issue: affects color of disabled elements.
 * 2. Correct font properties not being inherited.
 * 2. 修正字体属性不能被继承
 * 3. Address margins set differently in Firefox 4+, Safari, and Chrome.
 * 3. 处理margin值
 */

button,
input,
optgroup,
select,
textarea {
  color: inherit; /* 1 */
  font: inherit; /* 2 */
  margin: 0; /* 3 */
}

/**
 * Address `overflow` set to `hidden` in IE 8/9/10/11.
 * 修正 overflow被设置成hidden在IE 8/9/10/11
 * 参见IE的User Agent stylesheet: http://www.iecss.com/ (需翻墙)
 */

button {
  overflow: visible;
}

/**
 * Address inconsistent `text-transform` inheritance for `button` and `select`.
 * All other form control elements do not inherit `text-transform` values.
 * Correct `button` style inheritance in Firefox, IE 8/9/10/11, and Opera.
 * Correct `select` style inheritance in Firefox.
 */

button,
select {
  text-transform: none;
}

/**
 * 1. Avoid the WebKit bug in Android 4.0.* where (2) destroys native `audio`
 *    and `video` controls.
 * 2. Correct inability to style clickable `input` types in iOS.
 * 3. Improve usability and consistency of cursor style between image-type
 *    `input` and others.
 */

button,
html input[type="button"], /* 1 */
input[type="reset"],
input[type="submit"] {
  -webkit-appearance: button; /* 2 */
  cursor: pointer; /* 3 */
}

/**
 * Re-set default cursor for disabled elements.
 * 为disabled元素重新设置默认的cursor样式
 */

button[disabled],
html input[disabled] {
  cursor: default;
}

/**
 * Remove inner padding and border in Firefox 4+.
 * 删除内部补白和边框在FireFox 4+,可以使用最新版本FireBug查看FireFox系统样式forms.css
 * 也可以参考: http://mxr.mozilla.org/mozilla-central/source/layout/style/forms.css
 */

button::-moz-focus-inner,
input::-moz-focus-inner {
  border: 0;
  padding: 0;
}

/**
 * Address Firefox 4+ setting `line-height` on `input` using `!important` in
 * the UA stylesheet.
 * 什么是User Agent Stylesheet? http://www.zhihu.com/question/20549293
 */

input {
  line-height: normal;
}

/**
 * It's recommended that you don't attempt to style these elements.
 * Firefox's implementation doesn't respect box-sizing, padding, or width.
 *
 * 1. Address box sizing set to `content-box` in IE 8/9/10.
 * 1. 修正在IE8/9/10下box-sizing被设置成content-box
 * 2. Remove excess padding in IE 8/9/10.
 * 2. 删除多余的padding
 * 参考: http://www.iecss.com/
 */

input[type="checkbox"],
input[type="radio"] {
  box-sizing: border-box; /* 1 */
  padding: 0; /* 2 */
}

/**
 * Fix the cursor style for Chrome's increment/decrement buttons. For certain
 * `font-size` values of the `input`, it causes the cursor style of the
 * decrement button to change from `default` to `text`.
 * 
 * http://www.w3schools.com/html/tryit.asp?filename=tryhtml5_input_type_number
 */

input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
  height: auto;
}

/**
 * 1. Address `appearance` set to `searchfield` in Safari and Chrome.
 * 1. 修正appearance属性设置searchfield值在Safari和Chrome
 * 2. Address `box-sizing` set to `border-box` in Safari and Chrome
 * 2. 修正box-sizing设置border-box值在Safari和Chrome
 *    (include `-moz` to future-proof).
 * 参考 webkit默认的浏览器样式: http://trac.webkit.org/browser/trunk/Source/WebCore/css/html.css
 */

input[type="search"] {
  -webkit-appearance: textfield; /* 1 */
  -moz-box-sizing: content-box;
  -webkit-box-sizing: content-box; /* 2 */
  box-sizing: content-box;
}

/**
 * Remove inner padding and search cancel button in Safari and Chrome on OS X.
 * 在OS X的Safari和Chrome上删除search中的padding和cancel按钮
 * http://www.w3schools.com/html/tryit.asp?filename=tryhtml5_input_type_search
 * Safari (but not Chrome) clips the cancel button when the search input has
 * padding (and `textfield` appearance).
 */

input[type="search"]::-webkit-search-cancel-button,
input[type="search"]::-webkit-search-decoration {
  -webkit-appearance: none;
}

/**
 * Define consistent border, margin, and padding.
 * 定义一致的边框,外边距和内补白
 */

fieldset {
  border: 1px solid #c0c0c0;
  margin: 0 2px;
  padding: 0.35em 0.625em 0.75em;
}

/**
 * 1. Correct `color` not being inherited in IE 8/9/10/11.
 * 1. 修正在IE 8/9/10/11 `color`属性不能被继承
 * 2. Remove padding so people aren't caught out if they zero out fieldsets.
 * 2. 删除padding
 */

legend {
  border: 0; /* 1 */
  padding: 0; /* 2 */
}

/**
 * Remove default vertical scrollbar in IE 8/9/10/11.
 * 删除默认在IE 8/9/10/11的垂直滚动条
 * 参考IE的User Agent Style: http://www.iecss.com/ (可能需要翻墙)
 */

textarea {
  overflow: auto;
}

/**
 * Don't inherit the `font-weight` (applied by a rule above).
 * 不要继承font-weight
 * NOTE: the default cannot safely be changed in Chrome and Safari on OS X.
 * 注意: 默认值在OS X上的Chrome和Safari上不能安全的被修改(没有MAC,无法测试?)
 * http://www.w3schools.com/tags/tag_optgroup.asp
 */

optgroup {
  font-weight: bold;
}

/* Tables
   ========================================================================== */

/**
 * Remove most spacing between table cells.
 * 去除table cells之间的空隙
 */

table {
  border-collapse: collapse;
  border-spacing: 0;
}

td,
th {
  padding: 0;
}