2.2.6.1.2.2 Normal Style

At least one cell style (section 2.2.6.1.2) MUST be included in the STYLES (section 2.1.7.50) collection and this cell style (section 2.2.6.1.2) is called the normal style. The normal style MUST reference the first BrtXF (section 2.4.862) record in the CELLSTYLEXFS collection, and this BrtXF record MUST be a cell style XF (section 2.2.6.1.2.1), where the fStyle field equals 1.

The normal style, being the only required cell style, ensures that all cells have a cell style to reference. The normal style also provides a convenient object in which to store default cell formatting properties for an entire workbook, because all cells reference the normal style by default, until they are modified to reference a different cell style.