What is Website 404 Error?

Today we will learn HTTP errors, you will know what 404 errors are. In fact, there are almost a hundred different error codes. Don’t worry, you don’t have to memorize them all, but there are techniques to figure out roughly where the error is coming from.

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Why invent these numbers?

But why do we invent these error numbers? The answer is actually quite simple, when a user visits a website through his browser, the browser sends a request to the server according to the HTTP protocol. The server will also respond in HTTP format and if all goes well will send the requested resources (in our case the web page). But things get more complicated when there are errors. Knowing that there is a fault is good, but knowing where the error is is even better. This is why error numbers are quickly assigned to different types of errors. This is much more practical and saves time for many developers. For example, an error starting with 5 is a server level problem.

There are five types of errors

1.Information

2. Success

3. Redirects

4. User error

5. Server Error

So if the error number starts with 4, we know that the problem is from the user.

Why 404 error?

But why 404 error? The first number is 4, which is the error coming directly from the user and not from the server. Indeed, the 404 error means that the resource was not found, the server searched the user’s side but did not find it, so the error comes from the user who did not provide the correct url.

Discover 418 . error

HTTP 418 error has nothing to do with other errors. Indeed its meaning is “I am a teapot”. It has actually been a joke since it first appeared in RFC 2324 on April 1, 1998. The explanations given by the developers are: “There is coffee all over the world. . Increasingly, in a world where computers are ubiquitous, want to make coffee. Coffee making is an art, but the distributed wisdom of the web-connected world surpasses art. Therefore, there is a strong, rich demand for a clearly designed protocol for brewing coffee. Coffee is brewed using a coffee pot. Networked coffee makers require control protocols if they want to be controlled.”

In other words, the Hypertext Coffee Pot Control Protocol, or HTCPCP, aims to send an error back to everyone who wants to control the coffee pot remotely, telling them they’ve mistaken their address for… warm tea.

This April 1st “joke” became famous at the time, and its error code remained the same.

There are still people questioning this 418 error, even today.

Other HTTP Errors

For those who want to find a specific error, you can refer to the error tables categorized by category below.

Some of the code is still unused, but will be used in the future. The other codes don’t lead to any specific impressions to the user, but are still understandable (e.g. 200 or 304 codes, which the client never sees because they’re involved in the vast majority of successful requests. ).

All major HTTP errors are presented in these tables, of different error types:

Codes starting with 1 (Info):

Code	Message	Meaning
100	tiếp tục	Waiting to be processed.
101	Switching Protocols	Accept the protocol change.
102	Processing	In progress (avoiding the client to exceed the waiting period).
103	Early Hints	While waiting for the final response, the server returns links where the client can start downloading.

Codes starting with 2 (Success):

Code	Message	Meaning
200	OK	The request was processed successfully. The response will depend on the query method used.
201	Created	The request was processed successfully and the document was created.
202	Accepted	The request is processed, but the outcome is not guaranteed.
203	Non-Authoritative Information	Information returned, but generated by an uncertified source.
204	No Content	The request was processed successfully, but there is no information to return.
205	Reset Content	The request is processed successfully, the current page can be deleted.
206	Partial Content	Only part of the resource has been transmitted.
207	Multi-Status	Many answers. (WebDav)
208	Already Reported	Previous material has been submitted in this collection. (WebDav)
210	Content Different	The client-side copy of the resource is different from the server-side copy (content or property). (WebDav)
226	IM Used	The server completed the resource request, and the response is the representation of the result of one or more operations applied to the current result.

Codes starting with 3 (Redirect):

Code	Message	Meaning
300	Multiple Choices	The requested URI refers to some resource.
301	Moved Permanently	The document has been moved permanently.
302	Found	Document has been moved temporarily.
303	See Other	The answer to this request lies elsewhere.
304	Not Modified	The document has not been modified since the last request.
305	Use Proxy (since HTTP/1.1)	The request must be routed to the proxy.
306	Switch Proxy	Code used by older version of RFC 26167, now reserved. It means “The following requests must use the specified proxy”.
307	Temporary Redirect	The request must be temporarily redirected to the specified URI.
308	Permanent Redirect	The request must be permanently redirected to the specified URI.
310	Too many Redirects	The request must be redirected too many times or fall victim to a redirect loop.

Codes starting with 4 (web client error):

Code	Message	Meaning
400	Bad Request	The query syntax is wrong.
401	Unauthorized	Authentication is required to access the resource.
402	Payment Required	Payment is required to access resources.
403	Forbidden	The server understood the request, but refused to fulfill it. Unlike 401 errors, validation won’t make any difference. On servers that require authentication, this usually means that the authentication has been accepted, but access does not allow the client to access the resource.
404	Not Found	Resource not found.
405	Method Not Allowed	Unauthorized query method.
406	Not Acceptable	The requested resource is not available in a format that complies with the “Accept” header of the request.
407	Proxy Authentication Required	Access to the resource is allowed by identification with the proxy.
408	Request Time-out	The amount of time the request from the client has been waiting on the server side. According to the HTTP specification: “The client does not make a request while the server is ready to wait. The client MAY repeat the request without modification at any time afterwards.”
409	Conflict	The request could not be processed at this time.
410	Gone	The resource is no longer available and the redirect address is unknown.
411	Length Required	The length of the request is not specified.
412	Precondition Failed	The precondition sent by the request is not checked.
413	Request Entity Too Large	The requirement is too high.
414	Request-URI Too Long	URI is too long.
415	Unsupported Media Type	The query format is not supported for a certain method and resource.
416	Requested range unsatisfiable	The “scope” query header fields are incorrect.
417	Expectation failed	The behavior that is expected and defined in the header of the request is not satisfied.
418	I’m a teapot	“I am a teapot”: This code is defined in RFC 232410 of April 1, 1998, Hyper Text Coffee Pot Control Protocol. It’s a webmaster joke, intended to send a bug back to anyone who wants to remotely control a coffee pot, telling them they misplaced a teapot
421	Bad mapping / Misdirected Request	The request was sent to a server that was not able to generate a response (e.g. because the connection was reused).
422	Unprocessable entity	Entity provided with an incomprehensible or incomplete request. (WebDAV)
423	Locked	The operation cannot take place because the resource is locked. (WebDAV)
424	Method failure	A method in the transaction failed. (WebDAV)
425	Too Early	The server cannot process the request because it can be replayed.
426	Upgrade Required	The client should change the protocol e.g. to TLS/1.0.
428	Precondition Required	Requirements must be conditional.
429	Too Many Requests	The client made too many requests within a certain time frame.
431	Request Header Fields Too Large	The HTTP headers sent exceed the maximum size allowed by the server.
449	Retry With	Code defined by Microsoft. The request must be returned after performing an action.
450	Blocked by Windows Parental Controls	Microsoft Code. This error occurs when Windows Parental Controls is enabled and blocks access to the page.
451	Unavailable For Legal Reasons	This error code indicates that the requested resource is not accessible for legal reasons.
456	Unrecoverable Error	Unrecoverable error. (WebDAV)

Codes starting with 5 (Server Error):

Code	Message	Meaning
500	Internal Server Error	Internal server error.
501	Not Implemented	The requested function is not supported by the server.
502	Bad Gateway ou Proxy Error	By acting as a proxy or gateway server, the server receives an invalid response from the remote server.
503	Service Unavailable	The service is temporarily unavailable or under maintenance.
504	Gateway Time-out	Response timeout from server to intermediate server.
505	HTTP Version not supported	The HTTP version is not supported by the server.
506	Variant Also Negotiates	Negotiation error.
507	Insufficient storage	Not enough space to edit properties or build collections. (WebDAV)
508	Loop detected	Loop in a resource link. (WebDAV)
509	Bandwidth Limit Exceeded	Used by many servers to indicate over limit.
510	Not extended	The request does not respect the extended HTTP resource access policy.
511	Network authentication required	The client must authenticate to access the network. Used by fixed gateways to redirect clients to the authentication page.