bordertopwidth

bordertopwidth refers to the CSS property border-top-width, which sets the thickness of an element's top border. It is one of the individual border-width properties, along with border-right-width, border-bottom-width, and border-left-width. The value chosen for the top width can affect layout because borders contribute to the element’s overall size in the CSS box model.

Syntax and values: border-top-width: value; where value can be a length such as 2px, 0.5em, or one of the keywords thin, medium, or thick. The property only has a visual effect if the corresponding top border has a border-style other than none. If border-top-style is none or hidden, border-top-width has no visible effect even if a positive length is specified.

Default and inheritance: The initial value for border-top-width is medium. This property is not inherited by default; child elements do not automatically adopt the top border width of their parent.

Examples: border-top-width: 2px; border-top-width: thin; border-top-width: 0; These values illustrate explicit thickness, a keyword for relative sizing, and a zero width to remove the visible border (assuming the border-style allows visibility).

Usage notes: border-top-width is commonly used in combination with the other border-top properties (border-top-color and border-top-style) or in the shorthand border-top: value style color. It is widely supported across modern browsers and is a standard part of the CSS border module.

See also: border-top, border-top-color, border-top-style, border, box model, border-width shorthand.