402 – Payment Require
You are most likely attempting to visit a subscription page that requires you to pay; the authentication is usually in the form of a password obtained after you have successfully paid. If you are unable to access the site after you have paid, it may be that the Webmaster has yet to activate your account, or have had your account suspended for various reasons. In such case, contact the Webmaster.

403 – Forbidden
The web page you are trying to view is refusing public access because of its setting. It may be intentional, such as a private or personal page. Common message seen for a 403 error is “Access Denied.”

404 – Not Found
One of the most common errors, the 404 is an indication that the HTML page does not exist. Another common message of the error is “The Requested URL Was Not Found” or “File Not Found.” Recheck the URL. Mistyping the URL is a common mistake that that will incur this error.

406 – Not Acceptable
This error is caused when the web page could not be returned in a language, character set, or data format that the web browser can use.

407 – Proxy Authentication Required
This error indicates that you need to use a proxy server, which requires authentication credentials. This means you need to log in to the correct proxy server before you’re able to view the website.

408 – Request Timeout
Your connection to the server was drop. This occurs when the connection takes too long. This is usually caused by excess traffic load on either the server or the client. Reloading or refreshing the page will usually solve the problem. If that doesn’t work, try visiting the page again later.

409 – Conflict
The request submitted cannot be completed because it is conflicting with a rule established by the server.

410 – Gone
Pretty much no different from a 404 error, the 410 error suggests that the page has moved to another location. Double check the URL and try again.

411 – Length Required
This error is generated when the server fails to find the specific length information from the browser. This error is usually due to configuration or programming errors on the server end.

412 – Precondition Failed
A precondition specification on your browser’s HTTP data was not met. This is typically a configuration or programming error on the server end.

412 – Request Entity Too Large
A typical error when uploading a file that is exceeds the servers predefined limit. The error could be due to configuration or programming error on the server end. Try sending a smaller file size.

414 – Request URI Too Long
The Universal Resource Identifier (URI) exceeds the size the server can handle. A URL is a type of URI, so in the case of browsing the internet, it maybe that the URL is too long. This error is rare as servers can handle upwards of 2048 characters or 4096 characters.

415 – Unsupported Media Type
This error is produce when the server sees the browser is requesting a media that is not fully compatible with the request. This happens during data transfer, such as uploading a file using a method that the server can’t accept.

500 – Server Error
Also seen as “internal Error,” this is produced when the HTML cannot be retrieve and the server has no specifics on what the cause of the error is. Double check the URL and try refreshing or visiting the site again at a later time.

501 – Not Implemented
Server does not support the requested feature. This almost always is the result of an HTML coding problem or a possible version conflict.

502 – Bad Gateway
Also known as “Service Temporarily Overloaded,” this error indicates that the server is congested as too many people are trying to connect to the server. Try visiting the website again during non-peak hour.

503 – Service Unavailable
An indication that the server is currently down or overloaded. Try refreshing or simply returning to the site at a later time when the server is back up.

504 – Gateway Timeout
The server is taking too long to respond to the gateway server. This could be an indication that there is a communication problem with the gateway server or the web server. Try visiting the web page at a later time.

505 – HTTP Version Not Supported
This error when the server does not support the HTTP protocol used by the web browser.