To improve the usability of your website, you should always use a base font size of 16 CSS pixels. Furthermore, use sizes relative to the base size to define the typographic scale. It is common practice to use a line-height of 1.2em to have the proper vertical space between characters. Lastly, restrict the number of fonts used. Having too many fonts and font sizes can give your page layout a messy look.
Why you should use legible font sizes
Filed under: Documentation→Website Performance
Tags: font size, font sizes, mobile usability, usability, website performance