CSS3 圆角（border-radius）详解_html/css_WEB-ITnose
在做网页的时候，常常需要实现圆角，以前的做法就是切图，现在好了，有了css3的 border-radius 特性之后，实现边框圆角效果就非常简单了，而且其还有多个优点：一是减少网站维护工作量；二是提高了网站的性能，少了对图片的 HTTP 的请求，网页载入速度将变快；三是增加视觉美观性。
border-radius 是一种缩写方法。另外其四个值是按照top-left、top-right、bottom-right、bottom-left的顺序来设置的其主要会有下面几种情形出现：
1、只有一个值，那么 top-left、top-right、bottom-right、bottom-left 四个值相等。
2、有两个值，那么 top-left 等于 bottom-right，并且取第一个值；top-right 等于 bottom-left，并且取第二个值
3、有三个值，其中第一个值是设置top-left;而第二个值是 top-right 和 bottom-left 并且他们会相等,第三个值是设置 bottom-right。
4、有四个值，其中第一个值是设置 top-left 而第二个值是 top-right 第三个值 bottom-right 第四个值是设置 bottom-left。
其实 border-radius 和 border 属性一样，还可以把各个角单独拆分出来，也就是以下四种写法，这里我规纳一点，他们都是先Y轴在X轴，具体看下面：
border-top-left-radius: <length> <length> //左上角border-top-right-radius: <length> <length> //右上角border-bottom-right-radius:<length> <length> //右下角border-bottom-left-radius:<length> <length> //左下角
border-radius 只有在以下版本的浏览器：Firefox4.0+、Safari5.0+、Google Chrome 10.0+、Opera 10.5+、IE9+ 支持 border-radius 标准语法格式，对于老版的浏览器，border-radius 需要根据不同的浏览器内核添加不同的前缀，比说 Mozilla 内核需要加上“-moz”，而 Webkit 内核需要加上“-webkit”等，那么我为了能兼容各大内核的老版浏览器，我们看看 border-radius 在不同内核浏览器下的书写格式：
1、Mozilla(Firefox, Flock等浏览器)
-moz-border-radius-topleft: //左上角-moz-border-radius-topright: //右上角-moz-border-radius-bottomright: //右下角-moz-border-radius-bottomleft: //左下角
等价于：-moz-border-radius: //简写
2、WebKit (Safari, Chrome等浏览器)
-webkit-border-top-left-radius: //左上角-webkit-border-top-right-radius: //右上角-webkit-border-bottom-right-radius: //右下角-webkit-border-bottom-left-radius: // 左下角
等价于：-webkit-border-radius: //简写
3、Opera浏览器：
border-top-left-radius: //左上角border-top-right-radius: //右上角border-bottom-right-radius: //右下角border-bottom-left-radius: //左下角
等价于：border-radius: //简写
4、Trident (IE)
IE9 以下版本不支持 border-radius，而且 IE9 没有私有格式，都是用 border-radius，其写法和 Opera 是一样的，这里就不在重复。
为了不管是新版还是老版的各种内核浏览器都能支持 border-radius 属性，那么我们在具体应用中时需要把我们的 border-radius 格式改成：
-moz-border-radius: none | <length>{1,4} [/ <length>{1,4} ]? -webkit-border-radius: none | <length>{1,4} [/ <length>{1,4} ]? border-radius: none | <length>{1,4} [/ <length>{1,4} ]?其拆分开来的格式相应需要加上 -moz 和 -webkit，上面的代码其实就等价于下面的代码：
-moz-border-radius-topleft: <length> <length> //左上角-moz-border-radius-topright: <length> <length> //右上角-moz-border-radius-bottomright: <length> <length> //右下角-moz-border-radius-bottomleft: <length> <length> //左下角-webkit-border-top-left-radius: <length> <length> //左上角-webkit-border-top-right-radius: <length> <length> //右上角-webkit-border-bottom-right-radius: <length> <length> //右下角-webkit-border-bottom-left-radius: <length> <length> // 左下角border-top-left-radius: <length> <length> //左上角border-top-right-radius: <length> <length> //右上角border-bottom-right-radius: <length> <length> //右下角border-bottom-left-radius: <length> <length> //左下角
一般需求就如下：
.demo { width: 150px; height: 80px; border: 2px solid #f36; background: #ccc;}
但是有时候也需要拆分开来，如下：
.demo { border-top-left-radius: 10px 20px; border-top-right-radius: 15px 30px; border-bottom-right-radius: 20px 10px; border-bottom-left-radius: 30px 15px;}效果如下：
支持的浏览器：
如果想查看更详细的，链接地址：
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