Đặt outline style dạng đường liền (solid) bằng CSS

Dùng outline-style: solid.

Ví dụ

<html>
    <head></head>
    <body>
        <p style="outline-width:3px; outline-style:solid;">
            This text is having 3px solid outline.
        </p>
    </body>
</html>