2.2.58 [CSS-Level2-2009] Section 184.108.40.206, Fixed table layout
The width of the table is then the greater of the value of the 'width' property for the table element and the sum of the column widths (plus cell spacing or borders). If the table is wider than the columns, the extra space should be distributed over the columns.
Quirks Mode and IE7 Mode (All Versions)
The border-spacing property is not supported, so if a border-spacing value is specified it will not be taken into consideration when the table width is calculated. This includes when the border spacing is set to 0.
If a subsequent row has more columns than the greater of the number determined by the table-column elements and the number determined by the first row, then additional columns may not be rendered. CSS 2.1 does not define the width of the columns and the table if they are rendered. When using 'table-layout: fixed', authors should not omit columns from the first row.
All Document Modes (All Versions)
In a fixed-layout table, extra columns are rendered.