margin-left - CSS（层叠样式表）编辑

Summary

Area on which CSS margin-left apply margin-left 属性设置与元素相关联的盒子模型的左外边距。这个值可以为负值。

竖直排列相邻的两个盒子模型的外边距会重叠 margin collapsing。

在长度(width)被约束这种极少情况下，( 即当所有的宽度，左边界，边界，填充内容区域和边缘都被定义), 左边界会被忽略，如果被制定为auto值，会有相同的计算值。

初始值	`0`
适用元素	all elements, except elements with table `display` types other than `table-caption`, `table` and `inline-table`. It also applies to `::first-letter`.
是否是继承属性	否
Percentages	refer to the width of the containing block
适用媒体	visual
计算值	the percentage as specified or the absolute length
Animation type	a length
正规顺序	the unique non-ambiguous order defined by the formal grammar

Syntax

/* <length> values */
margin-left: 10px;  /* 绝对长度 */
margin-left: 1em;   /* 相对于字号的长度 */
margin-left: 5%;    /* 相对最近块元素的宽度 */

/* Keyword values */
margin-left: auto;

/* Global values */
margin-left: inherit;
margin-left: initial;
margin-left: unset;

Values

<length>

一个固定宽度 <length> 值 : 可以是一个绝对宽度, e.g. in px, 也可以是个相对宽度, e.g. in em, 或者相对视窗的大小, e.g. in vh.

<percentage>

百分比值 <percentage> 最近的块容器的宽度 width .

auto

auto关键词表示在当前布局模式下，浏览器根据接收的左边距自动计算出外边距。如果有几组margin-left和margin-right 设置为auto，那么最后计算的空间分布，会根据display，float，position属性，自动生成以下几种情况：

Value of `display`	Value of `float`	Value of `position`	Computed value of `auto`	Comment
`inline`, `inline-block`, `inline-table`	any	`static` or `relative`	`0`	Inline layout mode
`block`, `inline`, `inline-block`, `block`, `table`, `inline-table`, `list-item`, `table-caption`	any	`static` or `relative`	`0`, 除非`margin-left`和 `margin-right同时都设置为auto`. 这样的话，元素就被设置为基于父元素居中。	Block layout mode
`block`, `inline`, `inline-block`, `block`, `table`, `inline-table`, `list-item`, `table-caption`	`left` or `right`	`static` or `relative`	`0`	Block layout mode (floating element)
any `table-`, except* `table-caption`	any	any	`0`	Internal `table-*` elements don't have margins, use `border-spacing` instead
any, except `flex`, `inline-flex`, or `table-*`	any	`fixed` or `absolute`	`0`, except if both `margin-left` and `margin-right` are set to `auto`. In this case, it is set to the value centering the border area inside the available `width`, if fixed.	Absolutely positioned layout mode
`flex`, `inline-flex`	any	any	在水平方向上有空余空间的情况下，空余的空间会被平均分给水平方向上写有margin-left:auto属性的元素的外边距	Flexbox layout mode

Formal syntax

<length> | <percentage> | auto

Examples

.content { margin-left:   5%; }
.sidebox { margin-left: 10px; }
.logo    { margin-left: -5px; }

Specifications

Specification	Status	Comment
CSS Basic Box Model margin-left	Working Draft	No significant change from CSS 2.1.
CSS Transitions margin-left	Working Draft	Defines `margin-left` as animatable.
CSS Flexible Box Layout Module margin-left	Candidate Recommendation	Defines the behavior of `margin-left` on flex items.
CSS Level 2 (Revision 1) margin-left	Recommendation	Like in CSS1, but removes its effect on inline elements.
CSS Level 1 margin-left	Recommendation	Initial definition

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