Fixing Safari's min font size
from FreeForm Goodness comes the fix for Safari’s minimum font size, which changed in Safari 1.0. quoteHidden pref, your ass is mine.
defaults write com.apple.safari WebKitMinimumFontSize 9
defaults write com.apple.safari WebKitMinimumFixedFontSize 9
(you need to enter those two lines in the Terminal.)endquote