It's because the website is using cufon, a very early attempt at supporting custom fonts on the web using HTML canvas - basically every word you see is rendered as an image rather than text. The end result does not look good on hi-dpi screens like modern Macbook displays, probably they did not exist back then. The site mentions Google Font has a hosted version of it now and you can look at how it is meant to be rendered https://fonts.google.com/specimen/Averia+Libre