Some or all of the parts "<user>:<password>@", ":<password>",":<port>", and "/<url-path>" may be omitted. The scheme specific data start with a double slash "//" to indicate that it complies with the common Internet scheme syntax.
In real life, URLs look more like: http://www.apache.org/ — that is, there is no user and password pair, and there is no port. What happens?
A URL can be given more precision by attaching a port number: the web address http://www.apache.org doesn't include a port because it is port 80, the default, and the browser takes it for granted. If some other port is wanted, it is included in the URL after a colon — for example, http://www.apache.org:8000/. We will have more to do with ports later.
The URL always includes a path, even if is only /. If the path is left out by the careless user, most browsers put it back in. If the path were /some/where/foo.html on port 8000, the URL would be http://www.apache.org:8000/some/where/foo.html.
You should see text similar to that which follows.