Adjust `small` font size normalization
Make the font size for `small` not quite so small. The default value of `smaller` doesn't scale the base font size down by the same proportion whatever the base size. IE 6/7/8 end up rendering small text larger than most modern browsers. Opera can render it slightly smaller than Chrome and Firefox when the base font size is relatively large. The previous size of `75%` was a bit too small.