需求：用css設定漸變邊框
通過border-image來實現漸變色邊框

<div class="content"></div>

.content { 
	width: 100px;
    height: 100px;
    border:10px solid #ddd;
    border-image: -webkit-linear-gradient(red,yellow) 30 30;
   	border-image: -moz-linear-gradient(red,yellow) 30 30;
    border-image: linear-gradient(red,yellow) 30 30; 
}
 

效果如下：

但是border-image無法實現圓角，所以換一個思路：通過padding來實現，給父節點設定漸變背景，通過padding模擬邊框（此處的padding值就是border需要的值），注意父元素和子元素的border-radius屬性值保持一致。

<div class="content
	<div class="box"></div>
</div>

css

.content { 
	width: 100px; 
   	height: 100px; 
    box-sizing: border-box; 
    padding: 5px; 
    border-radius: 50%; 
    background-image: -webkit-linear-gradient(top, red 0%, blue 30%, yellow 60%, green 90%);  
    background-image: -moz-linear-gradient(top, red 0%, blue 30%, yellow 60%, green 90%); 
    background-image: linear-gradient(top, red 0%, blue 30%, yellow 60%, green 90%);  
}
.box { 
	width:100%; 
    height:100%; 
    border-radius:50%; 
    background:#fff; 
}
 

效果圖：