border-style

/* Specifies all four sides. */
div.test { border-style: dashed;}

/* Specifies top/bottom and left/right. */
div.test1 { border-style: dashed solid;}

/* Specifies top, left/right, and bottom. */
div.test2 { border-style: dashed solid dotted;}

/* Specifies top, right, bottom, and left individually. */
div.test3 { border-style: dashed solid dotted double;}

Value	Description
none	No border is drawn. The width also becomes 0. This is the initial value.
solid	Draws a single solid line border.
dashed	Draws a dashed border with larger gaps.
dotted	Draws a dotted border with smaller gaps.
double	Draws a border with two lines.
groove	Draws a border that looks carved in. Opposite of 'ridge'.
ridge	Draws a border that looks raised. Opposite of 'groove'.
inset	Draws a border that looks embedded. Opposite of 'outset'.
outset	Draws a border that looks raised outward. Opposite of 'inset'.

<div style="border-style: none; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>S

<div style="border-style: solid; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>

<div style="border-style: dashed; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>

<div style="border-style: dotted; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>

<div style="border-style: double; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>

<div style="border-style: groove; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>

<div style="border-style: ridge; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>

<div style="border-style: inset; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>

<div style="border-style: outset; height: 100px; padding: 10px; font-weight: bold;">A div element with height 100px and padding 10px.</div>

※ Version data based on MDN.

Specifies all border style properties at once.

If no value is set for 'border-style', it defaults to 'none'. With 'none', the border width becomes 0 and no border is drawn. To display any border, you must set 'border-style' to a value other than 'none'.