Because Web clients can vary so greatly (from small cell
phones to large color monitors, to ascii terminals, etc.),
and because the author today doesn't know what clients
users will use, we prefer not to prescribe design to
a single resolution. Instead, we recommend that authors
use technologies (such as style sheets) that allow them
to express their creativity, while also allowing users to
override settings such as font sizes when required to
meet their needs.
[There are other issues as well, such as variations in
readability of glyphs of different sizes in the world's
The W3C site tends not to specify any font sizes,
so that content is presented according to user preferences.