轮廓outline位于border外围，祈祷突出元素的作用；

　　outline-color

　　　　同border

　　outline-style

　　　　同border

　　outline-width

　　　　同border

 

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>outline</title>
    <style type="text/css">
        div{width:400px;height:50px;background:#eee;margin:100px auto;border: 5px solid blue;}
    </style>
</head>
<body>
    <div style="outline:10px dotted red;"></div>
    <div style="outline:10px dashed red;"></div>
    <div style="outline:10px solid red;"></div>
    <div style="outline:10px double red;"></div>
    <div style="outline:10px groove red;"></div>
    <div style="outline:10px ridge red;"></div>
    <div style="outline:10px inset red;"></div>
    <div style="outline:10px outset red;"></div>
</body>
</html>