I agree. Don't use font sizes relative to the viewport size. Furthermore, it is unlikely that anything should ever be relative to the vertical viewport size (ex

I agree. Don't use font sizes relative to the viewport size. Furthermore, it is unlikely that anything should ever be relative to the vertical viewport size (except in paged media, perhaps). Font sizes should not be relative to the horizontal or vertical viewport size. However, maybe there is exception if you want to set a maximum font size based on a percentage of the width so that all of the letters will fit. But, in my opinion it would usually be better to just avoid setting them by CSS anyways so that it uses the user settings or default settings instead, which should hopefully be set up for the specific display and user. (I often just disable CSS because of the mess they have made.)