# nav-down
**版本:CSS3**
### 语法:
**nav-down** : auto | <id>[ current | root | <target-name> ]? | inherit
**相关属性** : [nav-index](#) , [nav-up](#) , [nav-right](#) , [nav-down](#)
### 取值:
auto:User Agent默认的顺序。<id> :要切换元素的id命名。root | <target-name>:这个参数不能以”_”命名,指出frameset目标页面之间的元素焦点切换。如果指定的目标页面不存在,则被视为当前页面的焦点,意味着完全依赖框架页。该属性是以关键节点”root”标示,User agent将把整个frameset框架页定为目标。inherit:默认继承。
### 说明:
输入设备默认四个方向键按html文档顺序顺序来控制元素的焦点切换,但为了更好的用户体验,User agents提供了自定义切换焦点的控制顺序方向。
### 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_55e5d388c7d74.png" alt="IE" />Internet Explorer</th> <th class="type_firefox"><img src="https://box.kancloud.cn/2015-09-02_55e5d388d0d7f.png" alt="Firefox" />Firefox</th> <th class="type_chrome"><img src="https://box.kancloud.cn/2015-09-02_55e5d388d7e1e.png" alt="Chrome" />Chrome</th> <th class="type_opera"><img src="https://box.kancloud.cn/2015-09-02_55e5d388e168e.png" alt="Opera" />Opera</th> <th class="type_safari"><img src="https://box.kancloud.cn/2015-09-02_55e5d388e959c.png" alt="Safari" />Safari</th> </tr></thead><tbody><tr><td rowspan="4" class="version">版本</td> <td class="support yes"><span>(√)</span>IE6</td> <td class="support no"><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 yes"><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 yes"><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=utf-8" /><title>nav_相关属性测试</title></head><style>button { position:absolute; }button#b1 { top:0; left:50%; nav-index:1;nav-right:#b2; nav-left:#b4;nav-down:#b2; nav-up:#b4;}button#b2 { top:50%; left:100%; nav-index:2;nav-right:#b3; nav-left:#b1;nav-down:#b3; nav-up:#b1;}button#b3 { top:100%; left:50%; nav-index:3;nav-right:#b4; nav-left:#b2;nav-down:#b4; nav-up:#b2;}button#b4 { top:50%; left:0; nav-index:4;nav-right:#b1; nav-left:#b3;nav-down:#b1; nav-up:#b3;}</style><body> <button id="b1">BT1</button> <button id="b2">BT2</button> <button id="b3">BT3</button> <button id="b4">BT4</button></body></html>
复制代码
Copyright © 2009 [Tencent ISD webteam](http://webteam.tencent.com/). All Rights Reserved
### 快速跳转
- [语法](# "跳转到“语法”")
- [取值](# "跳转到“取值”")
- [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