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computer forensics

Computer Forensics Fields - A Brief Overview - Continue

The computer’s brain is considered to be the central processing unit or CPU for many people, but the analogy is not inaccurate, because the human brain can do so much more than the CPU. The...

computer forensics

Computer Forensics Fields - A Brief Overview

The computer forensics field, has helped the justice department lock up a lot of offenders, and as technology advances criminals, find it very hard to hide or delete incriminating data from a...

Data Compression

Data Compression is a Great Way to Reduce Data Size

The process which reduces data sizes, by removing excessive information is known as data compression. The size of a file is reduced, in order to save space, save time and reduce redundancy, during...


Converting A Binary Number to Decimal and to Hexadecimal

In order to be able to convert a decimal number to binary, one must have a basic understanding of the decimal, binary and hexadecimal numbering systems. Decimal numbers are used often in...

Agile Software Development

The Agile Software Development Methodology - Overview

On the article written by Hobbs and Petit, they explain that the agile software development methodology, has been gaining popularity, since the 2000s, and have taken software development by storm...

Mastering Cascading Style Sheet - Structuring Your Code - Document Type, DOCTYPE, Browsers and Validation


The website world, is an amazing world in which people are participants, all day every day, because people enjoy the time that they spend on the Internet.

Most people enjoy the Internet because, people get a lot out of the Internet, and find value on many websites, because the content on those websites, are valuable to people.

In today’s article, we are going to talk about document type, DOCTYPE, browsers and validation in terms of CSS3, in another series of CSS Mastery Structuring Your Code.

A set of rules which defines what is and isn’t allowed, in a particular XML or (X) HTML document, is known as a document type definition or DTD.

The machine readable rules, are then used by browsers, in order to parse a web page, to check the validity of the page, so that the web page can act accordingly.

A DTD and the version of the (X) HTML being used by a hypertext document, is known by the browser, when the page’s DOCTYPE declaration, is analyzed by the browser.

At the start of an (X) HTML document, there is a line or two of code known as the DOCTYPE declaration.

The DTD being used, by an (X) HTML document, is described by the DOCTYPE, which is declared at the top of the (X) HTLM document.

The specified DTD file, is accessed through a URL, which is typically, but not always included, in the DOCTYPE declaration.

Valid code, is usually needed, in order to write (X) HTML document, which would be correctly interpret by browser.

Usually browsers try to interpret the markup themselves, when the code is invalid.

However, browsers would usually not interpret an (X) HTML document, the right way; therefore, it is very important to write valid code, because browsers, would usually interpret an (X) HTML document the wrong way.

Sometimes, browsers will not display the (X) HTML document at all, if the code is not well written, even if the code is being sent with the correct MIME type.

MIME stands for Multipurpose Internet Mail Extensions, and it is known to be a way of identifying files on the Internet according to their nature and format.

A DOCTYPE declaration is required for the page to validate; therefore, browsers need to know which DTD to use in order to process an (X) HTML page correctly.

When you want to check your page, to know whether or not, it is valid then you need to use the W3C validator, a validator book market, or a plug-in validator found in browsers.

You can install a validator on your local machine as well, also many (X) HTML editors have a built in validator.

A validator usually tells you, whether or not your page validates, and if it’s not valid, then it will tell you why your page is not valid.

Validate your (X) HTML documents early and often, because it can help you to track down bugs, in your code.

But don’t think that validation is everything, and it can stall your development, it is important, but it should not slow the development of your website, down.

A degree of common sense is required to develop a website, and as long as you have that, you’ll be able to develop anything online.

Thank you, for reading this article!!!