public_htmldirectory can be used.
Note for addons developers : Note that clients won't download a file that they already downloaded unless you rename it.
resource.Addfile ( "/path/to/file.ext" ). However, some addon developers do not do this. In order for clients to download the required files, an lua file needs to be generated for it to work, which is what the lua enforcer feature does. The only downside is that clients may download files that are not required on the server.