2.1.117 [CSS-Level2-2009] Section 17.6.2, The collapsing border model

  • Article

V0284:

The specification states:

 UAs must compute an initial left and right border width for the table by examining 
 the first and last cells in the first row of the table. The left border width of 
 the table is half of the first cell's collapsed left border, and the right border 
 width of the table is half of the last cell's collapsed right border. If subsequent 
 rows have larger collapsed left and right borders, then any excess spills into the 
 margin area of the table.

Quirks Mode and IE7 Mode (All Versions)

The following clarifications apply:

  • If a table has a border set, that border overrides the cell border on the table edges.

  • If there is a cell border but no table border, the border width is not divided in half when calculating the border width in the collapsed model.

V0285:

The specification states:

 The top border width of the table is computed by examining all cells who collapse 
 their top borders with the top border of the table. The top border width of the 
 table is equal to half of the maximum collapsed top border. The bottom border width 
 is computed by examining all cells whose bottom borders collapse with the bottom of 
 the table. The bottom border width is equal to half of the maximum collapsed bottom 
 border.

Quirks Mode and IE7 Mode (All Versions)

The top and bottom widths of the table border are not computed via the specified methods. Instead, the border widths are 0.

V0286:

The specification states:

 Any borders that spill into the margin are taken into account when determining if 
 the table overflows some ancestor (see 'overflow').

Quirks Mode and IE7 Mode (All Versions)

Borders that spill into the margin overflow their ancestors.