CSS Border-Top Property
The border-top property defines the top border of an element. It is a shorthand that defines the style, width, and color of the top border. It is the combination of the following three properties:
It does not matter what order the values appear in. In addition, not all three values need to be present. If a value is not present, it will be set to the default. The default value for each property is as follows:
Note that the default value for border-top-style is "none," so if the border-top-style is not defined in border-top, no border will appear.
Example 1: All three values are defined
results in the following
Example 2: Only two values are defined
results in the following:
In Example 2, the width of the top border is not defined, so it is set to the default value of "medium."