<div class="classname"></div>
<div class="class1 ... classn"></div>

在一个元素上支持多个类。

.post-title {
    color: blue !important;
}

覆盖所有以前的样式规则。

h1 { } 
#job-title { }
div.hero { }
div > p { }

请参阅：选择器

color: #2a2aff;
color: green;
color: rgb(34, 12, 64, 0.6);
color: hsla(30 100% 50% / 0.6);

请参阅：颜色

背景

background-color: blue;
background-image: url("nyan-cat.gif");
background-image: url("../image.png");

请参阅：背景

.page-title {
    font-weight: bold;
    font-size: 30px;
    font-family: "Courier New";
}

请参阅：字体

.box {
    position: relative;
    top: 20px;
    left: 20px;
}

另见：位置

animation: 300ms linear 0s infinite;

animation: bounce 300ms linear infinite;

参见：动画

/* This is a single line comment */

/* This is a 
   multi-line comment */

div {
    display: flex;
    justify-content: center;
}
div {
    display: flex;
    justify-content: flex-start;
}

请参阅：弹性盒| 灵活技巧

#container {
  display: grid;
  grid: repeat(2, 60px) / auto-flow 80px;
}

#container > div {
  background-color: #8ca0ff;
  width: 50px;
  height: 50px;
}

请参阅：网格布局

counter-set: subsection;
counter-increment: subsection;
counter-reset: subsection 0;

:root {
  --bg-color: brown;
}
element {
  background-color: var(--bg-color);
}

请参阅：动态内容

另请参阅：类型 /类 / ID /通用 选择器

另请参阅： 相邻 /兄弟 /子 选择器

另请参阅：属性选择器

font-family: Arial, sans-serif;
font-size: 12pt;
letter-spacing: 0.02em;

@font-face {
    font-family: 'Glegoo';
    src: url('../Glegoo.woff');
}

color: red;
color: orange;
color: tan;
color: rebeccapurple;

color: #090;
color: #009900;
color: #090a;
color: #009900aa;

color: rgb(34, 12, 64, 0.6);
color: rgba(34, 12, 64, 0.6);
color: rgb(34 12 64 / 0.6);
color: rgba(34 12 64 / 0.3);
color: rgb(34.0 12 64 / 60%);
color: rgba(34.6 12 64 / 30%);

color: hsl(30, 100%, 50%, 0.6);
color: hsla(30, 100%, 50%, 0.6);
color: hsl(30 100% 50% / 0.6);
color: hsla(30 100% 50% / 0.6);
color: hsl(30.0 100% 50% / 60%);
color: hsla(30.2 100% 50% / 60%);

color: inherit;
color: initial;
color: unset;
color: transparent;

color: currentcolor; /* keyword */

.column {
    max-width: 200px;
    width: 500px;
}

另见：max-width  /min-width  / max-hight  /min-hight

.block-one {
    margin: 20px;
    padding: 10px;
}

另请参阅：margin  /padding

.container {
    box-sizing: border-box;}

另请参阅：box-sizing

.invisible-elements {
    visibility: hidden;
}

另见：visibility

div {
    margin: auto;
}

另见：margin

.small-block {
    overflow: scroll;
}

另见：overflow

.container {
  display: flex;
}

容器 Container

.container > div {
  flex: 1 1 auto;
}

.container > div {
  /* This: */
  flex: 1 0 auto;

  /* Is equivalent to this: */
  flex-grow: 1;
  flex-shrink: 0;
  flex-basis: auto;
  order: 1;
  align-self: flex-start;  /* left */
  margin-left: auto;       /* right */
}

.container {
  display: flex;
}

.container > div {
  width: 100px;
  height: 100px;
  margin: auto;
}

.container {
  display: flex;

  /* vertical */
  align-items: center; 

  /* horizontal */
  justify-content: center;
}

.container > .top {
 order: 1;
}

.container > .bottom {
 order: 2;
}

.container {
  display: flex;
  flex-direction: column;
}

.container > .top {
  flex: 0 0 100px;
}

.container > .content {
  flex: 1 0 auto;
}

一个固定高度的顶部栏和一个动态高度的内容区域。

.container {
  align-items: center;
}

垂直居中所有项目。

#grid-container {
    display: grid;
    width: 100px;
    grid-template-columns: 20px 20% 60%;
}

.grid {
    display: grid;
    width: 100px;
    grid-template-columns: 1fr 60px 1fr;
}

/*The distance between rows is 20px*/
/*The distance between columns is 10px*/
#grid-container {
    display: grid;
    grid-gap: 20px 10px;
}

#grid-container {
    display: block;
}

CSS 语法：

• 网格行：网格行开始/网格行结束；

例子

.item {
    grid-row: 1 / span 2;
}

#grid-container {
    display: inline-grid;
}

.grid {
    display: grid;
    grid-template-columns: 100px minmax(100px, 500px) 100px; 
}

CSS 语法：

• 网格行开始：自动|行行；
  
• 网格行端：自动|行行|跨度n；

例子

grid-row-start: 2;
grid-row-end: span 2;

grid-row-gap: length;

任何合法的长度值，如 px 或 %。0 是默认值

.item1 {
    grid-area: 2 / 1 / span 2 / span 3;
}

#container {
    display: grid;
    justify-items: center;
    grid-template-columns: 1fr;
    grid-template-rows: 1fr 1fr 1fr;
    grid-gap: 10px;
}

.item {
    grid-area: nav;
}
.grid-container {
    display: grid;
    grid-template-areas:
    'nav nav . .'
    'nav nav . .';
}

#grid-container {
    display: grid;
    justify-items: start;
}

.grid-items {
    justify-self: end;
}

网格项位于行的右侧（末尾）。

定义 CSS 变量

:root {
  --first-color: #16f;
  --second-color: #ff7;
}

变量用法

#firstParagraph {
  background-color: var(--first-color);
  color: var(--second-color);
}

另请参阅：CSS 变量

/* Set "my-counter" to 0 */
counter-set: my-counter;

/* Increment "my-counter" by 1 */
counter-increment: my-counter;

/* Decrement "my-counter" by 1 */
counter-increment: my-counter -1;

/* Reset "my-counter" to 0 */
counter-reset: my-counter;

另见：计数器集

body { counter-reset: section; }

h3::before {
  counter-increment: section; 
  content: "Section." counter(section);
}

ol {
  counter-reset: section;   
  list-style-type: none;
}

li::before {
  counter-increment: section;
  content: counters(section, ".") " "; 
}

html {
    scroll-behavior: smooth;
}

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