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HTTP - HyperText Transfer Protocol

http in a web address

HTTP is short for HyperText Transfer Protocol. HTTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands.

For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page. The other main standard that controls how the World Wide Web works is HTML, which covers how Web pages are formatted and displayed.

HTTP is a Stateless Protocol

HTTP is called a stateless protocol because each command is executed independently, without any knowledge of the commands that came before it. This is the main reason that it is difficult to implement Web sites that react intelligently to user input. This shortcoming of HTTP is being addressed in a number of new technologies, including ActiveX, Java, JavaScript and cookies.

HTTP Status Codes are Error Messages

Errors on the Internet can be quite frustrating — especially if you do not know the difference between a 404 error and a 502 error. These error messages, also called HTTP status codes are response codes given by Web servers and help identify the cause of the problem.

Recommended Reading: Learn the common HTTP status codes.

For example, "404 File Not Found" is a common HTTP status code. It means the Web server cannot find the file you requested. This means the webpage or other document you tried to load in your Web browser has either been moved or deleted, or you entered the wrong URL or document name.

Knowing the meaning of the HTTP status code can help you figure out what went wrong. On a 404 error, for example, you could look at the URL to see if a word looks misspelled, then correct it and try it again. If that doesn't work, backtrack by deleting information between each backslash, until you come to a page on that site that isn't a 404. From there you may be able to find the page you're looking for.

Custom 404 Error Pages

Many websites create custom 404 error pages that will help users locate a valid page or document within the website. For example, if you land on a 404 File Not Found page via Webopedia.com, a custom error page will load providing quick links to on-site navigation and site search features to help you find what you were looking for.

Webopedia 404 Error Page
Image: Webopedia's custom "404 File Not Found" (HTTP status code) page.

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