See documentation for the HTML 4.0 (XHTML) table model.
Width of space between cells in a table
Value | Meaning |
---|---|
A number | Thickness, measured in pixels. Although the NCBI Book DTD (or NCBI Collection DTD) can enforce only that this attribute contain any characters, validation beyond the DTD can constrain this value to a counting number (positive integer). |
Restriction: This attribute may be specified if the element is used. |