Paths in a URL aren't actually accessing files on a hard drive. They're sending a request to a program to serve the client the content defined by the path. Many

Paths in a URL aren't actually accessing files on a hard drive. They're sending a request to a program to serve the client the content defined by the path. Many times, said "server" program then goes and looks at a path on its host drive and serves a file there, but that is by no means a requirement - it's just a string that serves as an identifier. In this case, the content served in response to the identifier "/static/style.css" can very easily (and according to the author, is) baked directly into the (single) binary.