Looks like it's a special font provided by https://github.com/jdan/98.css (Which has come a long way in the past couple of years, despite still being 0.1.x)

Although there is a CSS rule for manipulating how fonts are anti-aliased, it was never standardized, and Firefox doesn't implement the vital no-smoothing option: https://developer.mozilla.org/en-US/docs/Web/CSS/font-smooth

Maybe with enough retro revivals it will receive attention.