The 4xx HTTP status codes are purposed to indicate what you or your client agent may have done wrong. In any case, your client agent is required to display the error to you especially when it is related to your actions. When a HEAD request is submitted, the server does not display the error code. Instead, it acts on the request.

400 - Bad Request

This is normally due to erred syntax or inclusion of characters that the server would not understand. This request will be displayed for your purposeful response.

The 3xx HTTP status codes are a class of status codes that indicate that further action by you may be required to get to the destination URL. Sometimes the web client may take some action on your behalf  if the consecutive request on the target URL is characterized by HEAD or GET. In the case where 5 consecutive URI's are all unavailable, the process is halted by most user agents to prevent a vicious cycle of redirection.

Redirect status codes are important to you because locations on the Internet are always changing, and sometimes the actions you take on the Internet may require a redirect to a new location. The request that your user agent makes may also require to return to the original URI after completing a certain step in the process. Using such codes, the web server and the user agent communicate to take you to other locations, either automatically - in mitigating errors or relocations, or basically - in responding to actionable requests.

Have you ever run into an annoying message ‘404 (requested page not found)’ while browsing through your website's monitoring results?

Well, that is just an example of the many HTTP status codes that exist. HTTP status codes refer to the responses a client gets from a server to a particular request. These codes are generated while a user tries to access a particular web page via a particular browser or while search engine spiders such as Googlebot make their way onto the page.

On the World Wide Web, one of the most common acronyms that you will encounter is HTTP, which stands for Hypertext Transfer Protocol. This is considered the center of data and information exchange on the web. HTTP is an application protocol that acts as a request-reply system that involves a client and a server. Request-reply or request-response is one of the simplest ways used by computers to communicate with each other. The original version of HTTP, officially called the HTTP/1.0 was revised into HTTP/1.1. However, since the inception of the first version, status codes have already been present.

One of the most prominent status codes is the 1xx, but before you get to know about what exactly 1xx is, it is important that you understand first what status codes are. In HTTP/1.0 and the subsequent versions of the protocol, whenever a request is performed, a response is triggered. The request methods include GET, HEAD, and POST. When the HTTP/1.1 came out, five new methods were introduced. These are OPTIONS, DELETE, TRACE, CONNECT, and PUT. Methods namely HEAD, GET, TRACE, and OPTIONS pose no harm to the server and thus, they are considered “safe methods.” On the other hand, POST, DELETE, and PUT may give adverse effects on the server and sometimes on transactions and other transmissions.