Here is the syntax for setting an element's border width:
| Property | Value | Notes |
| border-width: | thin | |
| border-width: | medium | The default border width |
| border-width: | thick | |
| border-width: | <length> | Set the border width to a specific length |
| border-top-width: | <length> | Set the top border |
| border-right-width: | <length> | Set the right border |
| border-bottom-width: | <length> | Set the bottom border |
| border-left-width: | <length> | Set the left border |
(The actual interpretation of thin, medium and thick is up to the browser.)