From the www-style style mailing list: "Maybe if browsers ship with a minimum font size . . . out of the box . . . web designers will realize that they have misunderstood what their readers want and that the browser window isn't something they control, but something they share with millions of other people." Bug 209879 gave this to Camino users. We should give this to all users. My personal preference is to set it to 11px. 11px is the closest integer under 70% applied to our 16px default. 70% is from https://bugzilla.mozilla.org/attachment.cgi?id=125604 as it would apply to http://lxr.mozilla.org/seamonkey/source/layout/style/nsStyleUtil.cpp#199 where we set the default scaling factor (sFontSizeFactors) for size xx-small. I realize this will break some pages that set container sizes in px, but believe that in effect those pages are already broken both when users have set their own minimums and/or when they zoom, since the resulting overlapping or hidden text really isn't any less useful than too small text.
Bug 286255 is same bug for Firefox
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