This attribute switches between two totally different box variants. When it
is present, a headlined box is created by the use of one single table but with
space GIFs. When this attribute is missing a standard box is created by the
use of two nested tables but without any space GIFs.
This sets the total table width in pixels. Default is no specific width for
the standard box and 300 pixels for the headlined box (because the headlined
variant needs to know a fixed size to create the GIFs accordingly).