Thank you very much for your kind words!
Indeed, it is Hoefler Text, as intended by the author of the web page. However, the default fonts set for my browser are very common: Arial, Times New Roman and Consolas. They are simply safe -- especially Arial -- as they provide almost all the glyphs one can need to render language-specific content properly. The rendering itself is performed by Infinality-patched fontconfig, and I am quite pleased with results.