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What is DHTML?

Aug 26, 2007
If you are creating a web site for the first time, then you probably have some knowledge of the HTML programming language. It is a fairly simple language to learn, and most beginning web designers are usually self-taught when it comes to using it for creating a simple web page. HTML provides the style, structure, and formatting for a web site.

However, HTML does not actually do anything. It is a static programming language. It does not process anything or make your site interactive, it just sits there and tells the browser how the site should look. So, other programming languages have been created to improve site design and make sites more interactive for the user.

One such language that has evolved is DHTML, a language that makes web pages both interactive and dynamic. It consists of several different components, including JavaScript, HTML, the Document Object Model (DOM) and Cascading Style Sheets (CSS). Using these, a web designer can control how the various elements of a web page are positioned and displayed within a web browser window. All pages designed with DHTML utilize client-side scripting, which means that the changes it initiates occur after the page has been fully loaded and viewing has begun. Server-side scripting languages, such as Perl and PHP, run on the server side before the page has finished loading.

Now we will examine each of the components of DHTML individually so that we can understand how this technology works. First, let us begin with the HTML. HTML is the principal language that is used to create web pages. It has been in use since the internet was first founded. To create a DHTML page, HTML 4.0 is used so that the structure of the page can be separated from the content through the use of the second component, style sheets.

Cascading style sheets specify how elements of a page are to be displayed. A cascading style sheet is normally an external file saved with a .css file extension and is uploaded with the rest of your web pages. This .css file specifies a layout for a webpage given certain tags and attributes. Then, all the programmer has to do is reference that .css file in the code for the webpage he or she is developing and just layout the webpage properly, and the .css file will automatically format all of the tags and attributes as specified. Specific styles can be applied to everything from paragraphs to email forms and much more.

The next component is the Document Object Model (DOM). This model is now compatible with most web browsers. It provides a standard set of objects that can be used in web programming, making it easier to access and change web documents. The Document Object Model looks at documents as a tree. Each of the elements within the document is regarded as a branch on a tree, and these elements can be accessed and modified through the DOM. Also, it is platform and language independent. This cross-platform compatibility is extremely significant because most wireless devices are now equipped with access to the internet and email. These wireless gadgets have installed on them web browsers and platforms that are not compatible with many elements of the basic HTML. The object model enables programmers to create documents that are structured in such a way that all web browsers will be able to display the document relatively equally, regardless of what sort of device is being used to view the web page. Also, it is compatible with all programming languages, including JavaScript, which is the final component we need to cover.

JavaScript, contrary to its name, has virtually nothing to do with the Java programming language. JavaScript is a scripting language. Scripting languages are used to connect diverse pre-existing parts to accomplish a new related task without compiling. Instead, scripting languages are interpreted, and are executed faster than a compiling language. JavaScript is very versatile and can communicate with other languages effectively. JavaScript is a registered trademark of Sun Microsystems, and is compatible with every major browser on the market.

JavaScript is most often used to handle certain events that might take place as the user interacts with the web page. For example, if the user is filling out an online form on the site and enters invalid information into one of the form fields, then JavaScript can be programmed into the website to check the validity of the input before the form is submitted. If the input is invalid, the script can be used to prevent the form from being submitted and to tell the user what needs to be corrected.

Now that you have some background on what DHTML is, you should enroll in some courses at a local computer programming institute if you have never studied it or its component parts before. You can also try accessing some online tutorials to learn the basics. Though there are certain drawbacks associated with using it because it is interpreted differently by each browser, you should still become familiar with DHTML and know how to use its different versions so that you can create dynamic web pages. The ability to design interactive web sites is a valuable skill for all web designers to have.
About the Author
Jim Pretin is the owner of http://www.forms4free.com, a service that helps programmers make email forms.
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