outline-offset

The outline-offset CSS property is used to set space between an outline and the edge or border of an element. An outline is a line that is drawn around elements, outside the border edge.

Example

<!DOCTYPE html>
<html>
    <head>
        <style>
            div {
                margin: 20px;
                width: 150px;
                padding: 10px;
                height: 70px;
                border: 2px solid black;
                outline: 2px solid red;
                outline-offset: 15px;
            }
        </style>
    </head>
    <body>
        <p>
            <b>Note:</b>
            Internet Explorer does not support the 
			outline-offset property.
        </p>
        <div>
            This div has an outline border 15px 
			outside the border edge.
        </div>
    </body>
</html>