The network server (which runs the Web site) considers that the HTTP data stream sent by the client (eg your web browser or our CheckUpDown robot) was correct, but access to the URL feature requires user authentication 1) not Was still provided or 2) that it was provided, but did not pass the authorization tests. This is commonly known as "HTTP Basic Authentication". The expected authentication request from the client is defined in the HTTP protocol as the WWW-Authenticate title field.
Usually this error message means that you need to register (register a valid user ID and password) somewhere first. If you have just registered them and then immediately see a 401 error, this means that your user ID or password or both were invalid for any reason (incorrectly entered, suspended user ID, etc.)
Repairing 401 Errors - General
Each Network Server manages user authentication in its own way. A security executive (eg, a Web Master) on the site usually decides which users are allowed to access the URL. This person then uses the network server software to establish these users and their passwords. So if you need to access the URL (or if you have forgotten your user ID or password), only the security executive on that site can help you. Forward any security problem directly to them.
If you feel that the web page of the URL "should" be accessible to everyone and various people on the Internet, then a 401 message indicates a more serious problem. The first thing you can do is check your URL through a web browser. This browser must be operating on a computer where you have never identified yourself before, and you should avoid the authentication (passwords, etc.) that you used earlier. Ideally, all of this must be done over an Internet connection that is completely different from any one you have used before (eg a different ISP dial-up connection). In summary, you are trying to get the same attitude that a complete stranger would have if you browsed the Internet to the web page.
If this type of browser check does not indicate any authorization problem, then it is possible that the network server (or nearby systems) have been configured to prohibit certain HTTP traffic patterns. In other words, http communication from a well-known network browser is allowed, but automated communication from other systems is refused with a 401 error code. This is unusual, but may indicate a very defensive security policy around the server from the Web.