My main browsers (FF and Chrome) are both configured for a 12 point font. In both browsers the font picker shows a font preview, and in both they are the same size and a comfortable size for reading web sites. My IE doesn't allow me to set font size, but seems to default to something a little bit larger than Chrome.
On my personal website, I use XHTML & CSS and have designated the page font as "medium", and use that font size for all of the principle text (the "content" text). When I view the site in IE 7, FF 3 and Chrome 0.4 the font displays as expected and matches the font pickers (except in IE where it's a little larger).
BUT, I go to nearly any other website (Google, StackOverflow, The DailyWTF, CodingHorror, Microsoft, Sourceforge, even W3C, etc) and they all display in tiny little microscopic fonts - what I estimate is 5 - 7 point.
This is true on 3 different computers, with 2 different O/S (Vista and XP) and 4 different monitors (laptop, CRT, and brand new WS LCD).
What's up with that? Am I overlooking something fundamental about web site design that I need to know? Or is it just that all these web sites do dumb things like setting the font to 50%, or 0.5 em, or x-small??? Why can't web site designers honor my font selection for the content text (I understand that side-bars, and footers and such might reasonably be small or x-small).
I would be tempted to think it's just uninformed web site designers, but, heck!, these are some big name sites!!
EDIT: To be clear I am not saying using em or % is dumb, I am wondering why many sites seem to use about 50% of my configured size. Surely my configured size is the size I would like to see text in.
EDIT: From W3C's CSS spec: "The following table provides user agent guidelines for the absolute-size mapping to HTML heading and absolute font-sizes. The 'medium' value is the user's preferred font size and is used as the reference middle value." - emphasis mine.
There's a consensus coming through that web sites base relative font sizes on the typical browser default of 16pt, which is unfortunate but "that's life". But what about other systems - can we expect all browsers to so default?
At least I understand the problem now.
I want to leave this question open for a while to see if others have differing views, before I select a final answer.
Conclusion: I have reset all my browsers to 16pt (18pt on my 125 DPI machines), and set my website to use font-size: 90%. This is giving a good display size and, of course, all my favorite sites are now readable. Thanks for all the constructive answers and the lively to and fro.
This is a great community.