People who use internet would have seen obviously this pg...;) when slower net connections exist... or when the website is not available that you search....
We know above 404 only.... Page Not Found! But it is just one among the pool... Others are the below ones..
Error 400 - Bad request.
Error 401 - unauthorized request.
Error 403 - forbidden.
Error 404 - Not found.
Error 500 -Internal error.
Error 501 - Not Implemented
Error 502 - Bad Gateway
Error 503 -Service unavailable.
Error 504 - Gateway Time-Out
Error 505 - HTTP Version not supported/DNS Lookup Fail/unknown host
Error 500-599 - Server Errors.