Hey OP, I notice you're using Berkeley Mono, which is beautiful. But your website's CSS appears to be applying boldface on an already boldface font in the headers (despite the typeface name claiming to be 'Regular', it is actually bold; see the datasheet[1]), which is causing bad hinting. Consider changing your typeface file!
[1]: https://cdn.berkeleygraphics.com/static/typefaces/berkeley-m...