What do I do if I get a 501 error on the Internet?
A 501 is HTTP status code for not implemented. This status code is received when the server does not support the facility required.
Note: A 501 error is not something you can fix, but rather will require a fix by the web server admin who manages the website and server you are trying to access.
Web server overload
If the server you're attempting to load is experiencing high demand it may be unable to complete your request and generate this error. If you're experiencing this error on a known good page, try loading the page again in a few minutes. If that is unsuccessful, try loading the page again later that day or the next day.
Web server errors
This error can also be encountered when the web server does not properly respond to the web browser's request or the program attempting to make a request with the web server.
Web server out of date
Finally, in some rare situations, the web server may need a software upgrade to properly communicate with your web browser or program.