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Internet censorship is control or suppression of the publishing of or access to information on the Internet. It may be carried out by governments or by private organizations either at the behest of government or on their own initiative. Individuals and organizations may engage in self-censorship on their own or due to intimidation and fear.

Internet privacy involves the desire or mandate of personal privacy concerning transactions or transmission of data via the Internet. It also involves the exercise of control over the type and amount of information revealed about a person on the Internet and who may access said information.

The referrer, or HTTP referrer — also known by the common misspelling referer that occurs as an HTTP header field — identifies, from the point of view of an Internet webpage or resource, the address of the webpage (commonly the Uniform Resource Locator (URL); the more-generic Uniform Resource Identifier (URI); or the internationalization and localization (i18n)-updated Internationalized Resource Identifier (IRI)) of the resource which links to it. By checking the referrer, the new webpage can see where the request originated.

The 404 or Not Found error message is a HTTP standard response code indicating that the client was able to communicate with the server, but the server could not find what was requested. A 404 error should not be confused with "server not found" or similar errors, in which a connection to the destination server could not be made at all. A 404 error indicates that the requested resource may be available again in the future.

The HTTP response status code 303 See Other is the correct manner in which to redirect web applications to a new URI, particularly after an HTTP POST has been performed.

The HTTP response status code 302 Found is the most common way of performing a redirection.

The HTTP response status code 301 Moved Permanently is used for permanent redirection.

In the HTTP protocol used on the World Wide Web, 403 Forbidden is an HTTP status code returned by a web server when a user requests a web page or media that the server does not allow them to. In other words, the server can be reached, but the server declined to allow access to the page.

The X-Forwarded-For (XFF) HTTP header field is a de facto standard for identifying the originating IP address of a client connecting to a web server through an HTTP proxy or load balancer. This is a non-RFC-standard request field which was introduced by the Squid caching proxy server's developers.

The HTTP Location header is returned in responses from an HTTP server under two circumstances: 1. To force a web browser to load a different web page. It is passed as part of the response by a web server when the requested URI has: Moved temporarily, or Moved permanently