|An opinion on browser font sizes - I think that websites that allow the user's browser font-size settings to have an influence (which really should be all) should arrange it so that the smallest relevant text on the page remains legible when the browser is set to 'smallest' font. This seems perhaps a little silly, in that it will give 'normal' users an unpleasantly large font, but that's what the setting is there for. You can adjust it as you see fit - but who would ever want to adjust a font to "so small that it can't be read because there aren't enough pixels"? The user configurable range should be from "very small and legible" to "big enough for a blind person". Any user-selected range should have its limits set at or before the point of unusable - there's no point in any font being smaller than legible (unless the content is usually irrelevant, as with my archive/comment links), and there's no point in any font being so large that it doesn't fit on the screen.|
So, from the point of view of an HTML-writer, the size one smaller than the CSS "x-small" should be the smallest you go. From the point of view of browser design, I quite like Phoenix's "smallest font" setting, which enables you to set a boundary cutoff to prevent pages dipping into illegibility. I'd like it even better if it went one step further, with an option for "smallest font" being done as an automatic adjustment to your overall font-size setting, such that every page's smallest font will be the stated size, and the other fonts on the page will be, proportionally, as they should be by the designer's layout. This would keep the design to its proper shape, but would allow for people with dull eyes or high resolution screens to keep the font legibly large, and for people with sharp eyes, low resolution screens, and an anti-aliasing-capable operating system to keep it usably small, consistently, regardless of the page designer's idea of what a good size would be.