Property Reference - CSS Reference - page 152

Name
border-top-width
Values:
thin | medium | thick | <length>
Initial value:
medium
Applies to:
All elements
Inherited:
No
Computed value:
Absolute length; 0 if the style of the border is none or hidden
Description:
Defines the width for the top border of an element, which will take effect only if the border's
style is something other than none . If the style is none , the width is effectively reset to 0 . Neg-
ative length values are not permitted.
Examples:
ul {border-top-width: 0.5in;}
h1 {border-top-width: 1px;}