Beauregard T. said:
If you design your site correctly, using my default size (100%) and
only specify { font-family: sans-serif; } you are catering to me, your
valuable visitor, rather than your own personal taste.
Actually, no. I'd be catering to your personal taste, rather than the
needs of the majority of my valuable visitors.
I consider setting default size (100%) to be a usability problem. In my
experience, most people are not comfortable reading default-sized text
(which is typically 16px/96ppi). Most people are also unfamiliar with
the font scaling controls in their browsers, and thus are unable to fix
things to their liking.
A far better solution is to size the font intelligently using
percentages or ems so that the chosen size suits the content of a given
page. People who need large type to read comfortably can still resize
it, and they are also more likely to know about the font scaling
controls, as they have a personal reason to look into it.
And remember, as stated so often, visitors with that famous operating
system component masquerading as a browser, will not easily be able to
up the font size for your site if you specified pixels.
If you'd read my post, you'd have noticed that I specifically advised
against using pixel-based font sizes, and recommended using percentages
or ems.