Notice that even the line mode browser centers H1 headings
and right justifies ADDRESS sections for example.
I think that Mosaic for X doesn't because the text widget
used doesn't have any justification or tabbing.
There is no reason why a browser should not have the
justufication style user-defined for each element.
Cello allows you to tailor a lot of things, maybe that,
(checks.) Not on my preprealpha version.
There have been a lot of advantges in sticking to the
logical markup rule. It has allowed lots of browsers
to be creative and flexible in presentation, and
has allowed for example TeX to be generated intelligently
from a set of HTML documents. If explicit markup had been
there, it would not have been possible.
Tim BL