# 结构性伪类 E:root
**版本：CSS3**
继承性：无
### 语法：
**E:root** ： {attribute}
**相关伪类**： [E:nth-child(n)](#) | [E:nth-last-child(n)](#) | [E:nth-of-type(n)](#) | [E:nth-last-of-type(n)](#) | [E:last-child](#) | [E:first-of-type](#) | [E:only-child](#) | [E:only-of-type](#) | [E:empty](#)
### 说明：
匹配文档的根元素。在HTML中，根元素永远是HTML
### 兼容性：
<table><thead><tr><th class="type">类型</th> <th class="type_ie"><img src="https://box.kancloud.cn/2015-09-02_55e5d38e7c0e6.png" alt="IE" />Internet Explorer</th> <th class="type_firefox"><img src="https://box.kancloud.cn/2015-09-02_55e5d38e85d05.png" alt="Firefox" />Firefox</th> <th class="type_chrome"><img src="https://box.kancloud.cn/2015-09-02_55e5d38e8dcd3.png" alt="Chrome" />Chrome</th> <th class="type_opera"><img src="https://box.kancloud.cn/2015-09-02_55e5d38e96681.png" alt="Opera" />Opera</th> <th class="type_safari"><img src="https://box.kancloud.cn/2015-09-02_55e5d38e9d9e1.png" alt="Safari" />Safari</th> </tr></thead><tbody><tr><td rowspan="4" class="version">版本</td> <td class="support no"><span>(×)</span>IE6</td> <td class="support yes"><span>(√)</span>Firefox 2.0</td> <td class="support yes"><span>(√)</span>Chrome 1.0.x</td> <td class="support yes"><span>(√)</span>Opera 9.63</td> <td class="support yes"><span>(√)</span>Safari 3.1</td> </tr><tr><td class="support no"><span>(×)</span>IE7</td> <td class="support yes"><span>(√)</span>Firefox 3.0</td> <td class="support yes"><span>(√)</span>Chrome 2.0.x</td> <td></td> <td class="support yes"><span>(√)</span>Safari 4Public beta</td> </tr><tr><td class="support no"><span>(×)</span>IE8</td> <td class="support yes"><span>(√)</span>Firefox 3.5</td> <td></td> <td></td> <td></td> </tr><tr><td></td> <td></td> <td></td> <td></td> <td></td> </tr></tbody></table>
### 示例：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" /><style type="text/css">html:root {background-color:#DCDCDC;}</style><title>结构性伪类 E:root</title></head><body><div style="width:733px; border: 1px solid #666; padding:5px;"><p>结构性伪类 E:root</p></div></body></html>
复制代码
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### 快速跳转
- [语法](# "跳转到“语法”")
- [说明](# "跳转到“说明”")
- [兼容性](# "跳转到“兼容性”")
- [示例](# "跳转到“示例”")
- CSS3 Properties
- 边框(Border)
- Border-color
- Border-image
- Border-radius
- box-shadow
- 背景(Background)
- background-origin
- background-clip
- Background-size
- Multiple backgrounds
- 颜色(Color)
- HSL colors
- HSLA colors
- opacity
- RGBA colors
- 文本(Text effects)
- text-shadow
- text-overflow
- word-wrap
- 用户界面(User-interface)
- box-sizing
- resize
- outline
- outline-width
- outline-style
- outline-offset
- outline-color
- nav-index
- nav-up
- nav-right
- nav-down
- nav-left
- 基础盒模型(Basic box model)
- overflow
- overflow-x
- overflow-y
- 内容(Generated Content)
- content
- 其它模块(Other modules)
- media queries
- Speech
- columns
- column-width
- column-span
- column-rule
- column-rule-color
- column-rule-width
- column-rule-style
- column-gap
- column-fill
- column-count
- column-break-before
- column-break-after
- @font-face
- 选择器(selectors)
- 子串匹配的属性选择符 E[att^="val"]
- 子串匹配的属性选择符 E[att$="val"]
- 子串匹配的属性选择符 E[att*="val"]
- 结构性伪类 E:root
- 结构性伪类 E:nth-child(n)
- 结构性伪类 E:nth-last-child(n)
- 结构性伪类 E:nth-of-type(n)
- 结构性伪类 E:nth-last-of-type(n)
- 结构性伪类 E:last-child
- 结构性伪类 E:first-of-type
- 结构性伪类 E:only-child
- 结构性伪类 E:only-of-type
- 结构性伪类 E:empty
- UI元素状态伪类 E:checked
- UI元素状态伪类 E:enabled
- UI元素状态伪类 E:disabled
- UI元素状态伪类 E::selection
- 否定伪类 E:not(s)
- 目标伪类 E:target
- 通用兄弟元素选择器 E ~ F