The most common HTTP status errors

The most common HTTP status code, 500 Internal Server Error.
This error is pretty much self descriptive but also very generic server error. It could be caused by the misconfiguration on the server, the server is overloaded due to high volume of traffic, or the server is currently under maintenance, etc.

The second most common HTTP status code, 404 Not Found.
This means the requested resource, usually a file on the server is not found. For example, after you entered an URL on the browser, it requests certain files on the server to return a web page, but all of some of the files on the server that suppose to serve the web page is not there. Thus the server give back a 404 not found HTTP status code. This usually happens when you mistyped an URL, you bookmarked the URL but the URL for the webpage has been changed recently by the website owner, or source code on the server has been moved but the old links has been cached either by your browser or the server. In case of cache issue, you can clear your browser cache or put some dummy parameters after the url such as “?abcdefg” at the end and try again.

HTTP status code starts with 4, or the 4XX class of HTTP status codes are client side errors due to invalid requests. Among them 404 is the most common one. The others are 400 Bad Request, 401 Unauthorized, 403 Forbidden, etc.

HTTP status code starts with 5, or the 5XX class of HTTP status codes are server side errors due to various server issues. Among them 500 is the most common one. The others are 501 Not Implemented, 502 Bad Gateway, 503 Service Unavailable, 504 Gateway Timeout, etc.