Like border-style, but for the top border only.
default
border-top-style: none;
Removes the top border.
border-top-style: dotted;
Turns the top border into a sequence of dots.
border-top-style: dashed;
Turns the top border into a sequence of dashes.
border-top-style: solid;
Turns the top border into a solid line.
border-top-style: double;
Splits the top border into two lines.
border-top-style: groove;
Sets an inset style to the top border.