Common Server Errors
An internal server error is an error on the web server you're trying to access. That server is misconfigured in some way that prevents it from responding properly to what you're asking it to do.
Unauthorised response generally occurs when there is a problem with the credentials used or the completeness of the HTTP POST.
If there is an attempt to access a forbidden directory on a website you will see this error message which means there is no login opportunity on the page.
“404 Not Found”
A 404 not found error is an HTTP status code that means that the page you wanted to access a website couldn't be found on their server.
“500 Internal Server Error”
Perhaps one of the most common message, indicates a generic server error that’s displayed when the server cannot determine the exact problem.
“502 Bad Gateway”
This occurs when the server is operating as a gateway or proxy server and the upstream server returns an invalid response.
“301 Moved Permanently”
Moved Permanently redirect status response code indicates that the resource requested has been definitively moved to the URL given by the Location headers
302 Found is a common way of performing URL redirection. This is an invitation to the user agent (e.g. a web browser) to make a second, otherwise identical, request to the new URL specified in the location field.
How to check if a website is down or you have a local problem i.e. such as Cache or ISP