You may have noticed that sometimes 4D creates a folder "WebFolder" next to the structure file. Why and when is it created?
If you display the Publishing page of the Web section in the Preferences you will notice that a path to a default Web folder and index HTML file is provided:
If when the database is opened, this folder and file do not exist, 4D takes notice of it. If you then start 4D's Web server, 4D creates that file and folder so that a basic HTML page is sent when users connect.