CSS: border-collapse

Specifies whether the borders for an element are collapsed or separated.

Browser/User Agent Support

IE Netscape Mozilla Opera Safari
5.0+ 6.0+ 1.0+ 5.0+ 1.2+
IE: In IE 5, 6, and 7, border-collapse: collapse does not overrule cellspacing.

IE	Netscape	Mozilla	Opera	Safari
5.0+	6.0+	1.0+	5.0+	1.2+
IE: In IE 5, 6, and 7, border-collapse: collapse does not overrule cellspacing.

[collapse-style-value]

inherit Inherit the value from the parent element.
collapse No spacing between borders.
separate Spacing between borders.

For a demonstration of the border-collapse attribute, see the demo page on quirksmode:

W3C CSS2

inherit	Inherit the value from the parent element.
collapse	No spacing between borders.
separate	Spacing between borders.