When the font-size is defined on html instead of body, Safari flickers
the font size back and forth when resizing around each font-size change.
Easy workaround is to change the font-size on body instead.
It doesn't make much difference since it has `width: 100%;`, but I needed `<hr>` between columns on <=640px screens, and that `<hr>` is visible only on those screens, removing float allowed me to use margins correctly on `<hr>` element to set some spacing between elements.