HTTP error codes are an unavoidable communication language throughout the entire website design and maintenance process. They represent the feedback from the server and browser, not only indicating the result of request processing but also implying potential problems in the website's architecture, program development, and content management. For businesses, frequent HTTP errors not only severely impact user experience and reduce user retention rates but can also weaken search engine trust, affecting website ranking and traffic. East Tech, a professional website development expert with 17 years of experience, will today systematically analyze the most common HTTP error codes in website design, revealing their underlying causes, solutions, and prevention strategies to help businesses better maintain stable website operation.

First, it's important to understand that HTTP error codes are typically categorized by three digits, with different first digits corresponding to different error types: 1xx represents a message response (request received, processing continues), 2xx represents a success response (request successfully processed), 3xx represents a redirect (further action is required to complete the request), 4xx represents a client-side error (the request contains an error, the server cannot process it), and 5xx represents a server-side error (the server encountered an error while processing a legitimate request). Among these, the 4xx and 5xx series are the most frequently encountered error types in website design and maintenance, and are also the core source of problems affecting user experience.

Codes 301 and 302

While technically not error codes, you'll see them frequently when browsing the web. HTTP 301 and 302 are both redirect codes, indicating that the page has been permanently (301) or temporarily (302) moved for some reason. If you're using WordPress, setting up redirects is very simple, as there are many very reliable plugins that can handle all of these for you. If not, simply adjust your .htaccess file.

Error 400

A 400 error is one of the HTTP error codes that a user might be able to resolve. They are the ones making the request incorrect. It's not that the requested URL is missing or forbidden, but rather that the request itself is somehow garbled or corrupted, and the server simply cannot understand it.

Error 401

A 401 error is sent whenever there's a problem verifying browser credentials. There are several ways to resolve this, both on the user's end and on the server administrator's end. Receiving a 401 error is not like being told your login information is incorrect. This is a step or two higher because the server itself cannot verify your request, meaning it could be a DNS problem or a corrupted cookie, etc.

Error 403

A 403 error is actually one of the very common HTTP error codes. For some reason, the server you're trying to access doesn't allow you to access it at the root level. There's a permission problem with some file or token while trying to process your request. The problem with troubleshooting HTTP 403 is that tracing the cause of the corrupted credentials is often more important than restoring them to their original state.

Error 404

This is definitely the most common of all HTTP error codes. The 404 Not Found status code means: the website cannot find your request. This is different from 401 because your request might be perfectly reliable. It means the server cannot find the media. It understands something should be where you want it to be, but it doesn't know why it's empty.

Error 410

Don't confuse 410 with 404. While both are given when something is missing, a 410 error means it's gone forever. You can actually intentionally provide a 410 status code, for example, if you delete a page and don't intend to replace it. Search engines will know to stop indexing that particular content, whereas this doesn't happen with 404. Think of 404 as you misplaced your keys, while 410 is like throwing them into the sea. Either way, they're gone, but this one is more serious.

Error 500

Unlike some HTTP error codes, users usually don't play any role in displaying a 500 error. This is an internal server error, meaning that somewhere in your website's file system, something isn't being resolved. There are many reasons why internal server errors can occur, and just as many solutions.

Error 501

As an internet user, you can't fix a 501 error. It's entirely server-side, and what you should do is contact your website administrator and let them know that their server is returning 501 errors. That said, as a website owner, 501 means your website is down or offline. When someone makes a request to the website, the host returns an unfulfilled error because, at that point, the functionality to complete the request simply doesn't exist.

Error 502

A 502 Bad Gateway error is another status code that can be caused by a range of different reasons. This means that an invalid response was given at some node (gateway) on the way to your website. Sometimes you can find this error by running traceroute, but as with many causes, there are many solutions. From resetting your browser cache to DNS settings, or even refreshing your CDN and resetting it, it's a process of trial and error to find out the actual location of the faulty gateway.

Error 503

Many times, a 503 HTTP error will simply disappear on its own. This is different from most HTTP error codes. A 503 Service Unavailable error means it doesn't disappear, it just takes a short break. Perhaps your website is down for maintenance or upgrades, a script is taking too long to execute, it's using too much memory, or something similar is happening. It will disappear after a few minutes. However, if it doesn't disappear and your service is still unavailable, it likely boils down to resetting your server, resetting your firewall, or even checking the routes to your server, as one of the nodes delivering the information may be down for maintenance. We've looked at a long list of solutions and causes for HTTP 503 errors so that if your server is temporarily unavailable, it's still a temporary problem.

Error 504

You may have received a 504 error without even realizing it. Often, a 504 error is simply listed by the browser as "This page is invalid." This means your connection has been trying to access the server for too long, and it just isn't responding. The connection has simply timed out. In most cases, this comes from your hosting provider or CDN. Users usually can't fix it, but as an administrator, you need to go in and adjust your proxy settings, ensure your domain settings are correct (correct name, server, etc.).

Error 508

The HTTP 508 error is a resource limit reached error. Again, users are (usually) not involved. They won't consume your resources by trying to refresh your page too many times. A 508 occurs when your server is overloaded for a variety of reasons. It could be insufficient memory. Perhaps the bandwidth is congested with heavy traffic. Perhaps you are under a DDoS attack. Whatever the reason, your server doesn't actually have the physical resources to satisfy the user's request. Nobody wants this to happen.

HTTP Error Code Summary

This is an introduction to HTTP error codes. This isn't even all of them. These are just the most common ones. If you'd like to delve deeper into some of the more obscure aspects of data transfer on the Internet, we highly recommend checking out the documentation on this topic from the Developer Network.

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