3.4 Relative rather than absolute units
The New Zealand Web Standards 2.0 were released in March 2009 and replace the previous version, the New Zealand Government Web Standards 1.0 (below). See Meeting the standards for more information.
The Standard
3.4 Use relative rather than absolute units in mark-up language attribute values and style sheet property values
Guide to this Standard
Avoid fonts with sizing based on absolute units such as points (pt), pixels (px), centimeters (cm), millimeters (mm) and inches (in). Font sizes expressed as percentages (%) and "ems" (em) are preferred.
A base size font across the whole web site (for consistency) is recommended.
This standard covers the WAI checkpoint 3.4 for NZ government agencies.
Rationale for this Standard
People with visual disabilities may have difficulty reading text, or not be able to read text at all. If the cause of the reading difficulty is principally due to the user considering the text too small, most browsers will allow the enlargement of fonts. Some browsers enable scalable enlargement of the whole document (i.e. Opera). However, most browsers will more likely resize relatively-sized fonts than absolutely-sized fonts. Most browsers will attempt resizing with absolute fonts but the resulting web site pages will often end up with an undesired overlap of content upon enlargement.
This is detailed on the Irish National Disability Authority site.
