This diagram shows the effect of the 'collapse' value of the 'border-collapse' property.
The diagram shows three cells in the same row and the grid lines that separate them. The left and right content, padding, border, and margin areas of each cell are labeled by rotated text above each of the areas. Each (red, dotted) grid line bisects the border between two cells.
The table width is indicated below the cells as encompassing all the left and right content, padding, border, and margin areas of the cells, except for the cells that touch the sides of the table. In this case, only half the exterior border widths are counted in the table's width.