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[CSS3 tutorial] Detailed explanation of relative unit rem_html/css_WEB-ITnose
[CSS3 tutorial] Detailed explanation of relative unit rem_html/css_WEB-ITnose
作者：zhanhailiang 日期：2015-01-28
定义
CSS3新增了一个相对单位rem，其官方定义如下：
font size of the root element
rem，em，px单位的区别
rem单位和em单位都是相对大小，px是绝对大小。其区别在
- em基于当前元素的(如果没设置就是继承其父元素的)font-size，这样会出现一些组合问题；
- rem则是只相对于根元素的font-size，即只需要设置根元素的font-size，其它元素使用rem单位设置成相应的百分比即可；
兼容性说明
目前，除了IE8及更早版本外，所有浏览器均已支持rem。对于不支持它的浏览器，应对方法也很简单，就是多写一个绝对单位的声明。这些浏览器会忽略用rem设定的字体大小。
示例
<html><head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <style> /*浏览器默认font-size:16px;*/ /*%单位对于font-size、line-height等，是基于其父元素的font-size;*/ /*16px * 312.5% = 50px;*/ html{font-size: 312.5%;} /*50px * 0.5 = 25px; IE8及之前版本使用*/ body{font-size: 0.5rem; font-size\0:25px;} /*50px * 0.25 = 12px; IE8及之前版本使用*/ p{font-size: 0.25rem; font-size\0:12px;} </style></head><body>浏览器默认font-size:16px;<p> 浏览器默认font-size:16px;</p></body>更多阅读
- (W3C)EM, PX, PT, CM, IN…
- 理解css中的长度单位
- CSS3教程:相对单位rem详解
- IE8 HACK介绍
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