When you browse the web, your browser is the client that connects to the web server of a particular website through HTTP protocol.
Everything in this process occurs through a network connection which enables web servers to send response data to the client (your browser) such as:
- Content of the web pages
- Protocol control information
- Status codes
It’s quite likely that at some point, you won’t be able to visit the website, and instead, you will see an error or an actual status code.
For each request that your browser sends to the web server – the web server sends back status code that indicates the result of the request.
These status codes contain three digits and are separated into several categories:
100-199: informational state
200-299: success state
300-399: redirection state
400-499: client (your browser) errors
500-599: server (web server) errors
To avoid confusion, you can only see some of the possible errors and status codes. Codes that are part of an error are typically displayed right on the website as you try to visit it (the request will fail).
Here are some of the most frequent errors and status codes you can see today on the web:
This status code was added in HTTP 1.1 version of the protocol, and it allows the client (browser) to send a tiny, particular packet that asks the server to reply with a 100 code.
Once the server responds, the client will send a more significant follow-up request. This is designed for the server to be able to confirm it can receive large requests.
This status code means that the web server processed the request from your browser successfully and sent the webpage content to it.
The majority of HTTP requests result in this status code, and you won’t see it often as the web browser usually shows errors when something is broken.
301 Moved Permanently
You can usually see this status code when URI you’re trying to load is moved to a different location. This is done by using the redirection feature, which allows your browser to automatically follow the redirect and load the page from a new place without any input on your end.
302 Found/307 Temporary Redirect
This is also a status code related to redirection. Still, in this case – you are being redirected temporarily instead of permanently. Usually, temporary redirection is only used when there’s active maintenance on the server.
Your browser also follows this redirect automatically, like with 301 redirects.
400 Bad Request
This error means that there was a syntax problem with the client (your browser) and the web server couldn’t understand the request. This is likely a glitch with your browser, or it could be network on either end.
This error indicates that your web browser isn’t allowed to access the page unless it authenticates with proper credentials (username and password).
This error means that you don’t have permissions to access the page in question on the server. It could be set up intentionally, or it could be a permission or set up problem on the server and website itself.
404 Not Found
If you see this error in your browser – it means that the web server couldn’t find the page/file you were looking for. 404 error means that the network connection between the client and the server is fine, so it usually occurs when a person types in a wrong URL or the file/page was removed, and the administrator didn’t set up the proper redirect.
If you stumble upon this error – make sure to re-check the URL you’re visiting or wait until the server administrator fixes the problem.
500 Internal Server Error
When 500 Internal Server Error occurs – it means that your browser correctly sent the request to the web server, but the web server wasn’t able to process it properly. This error is related to a server problem such as low memory or disk space, and only server administrators can fix it.
502 Bad Gateway
This error commonly occurs when there’s a network connection problem between the client and the server. It can be related to network firewall configuration issues and your router.
503 Service Unavailable
This error means that the web server can’t process the request from your web browser. It also indicates that this is a server-side issue, and it needs to be fixed by the server administrator.
Usually, web servers use 503 errors to indicate that account exceeded resources, such as disk space, concurrent users or bandwidth.