This site is built with basic html and javascript. It utilizes a W3.CSS template to add some basic styling. The w3.CSS reference is available at https://www.w3schools.com/w3css/w3css_references.asp
The map components use Leaflet https://leafletjs.com/ and at this time are mostly generated from the folium python library https://python-visualization.github.io/folium/latest/reference.html .