原理是通过定位把以前的样式覆盖掉，就酱...

代码如下：

css  .checkbox        {            position: relative;            padding-left: 8px;        }        .checkbox:before{            content: '';            display: inline-block;            width: 16px;            height: 16px;            border: 2px solid #999;            border-radius: 50%;            background: #fff;            position: absolute;        }        input[type=checkbox]:checked:before{            content: '';            display: inline-block;            width: 8px;            height: 8px;            border-radius: 100%;            background: #999;            position: absolute;            top: 5px;            left: 13px;        }        input[type=checkbox]{            margin-right: 6px;        }

html
改变单选或者复选框的样式    11    22