The border-bottom-style property in 
border-bottom-style: none|hidden|dotted|dashed|solid|double|groove|ridge|inset|outset|initial|inherit;
none: The default value. none specifies that there is no border.
hidden: The same as none.
dashed: Specifies that the border is dashed.
dotted: Specifies that the border is dotted.
double: Specifies that the border is double.
solid: Specifies that the border is solid.
groove: Specifies a 3D grooved border.
ridge: Specifies a 3D ridged border.
inset: Specifies a 3D inset border.
outset: Specifies a 3D outset border.
initial: Sets the value to its default value.
inherit: Inherits property from its parent value.
The code below demonstrates the use of the border-bottom-style property.