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Q.A few years back, I remember reading about Dynamic HTML. What is it and how is it different than regular HTML? Is it widely used in Web sites today? Where can I learn more about DHTML?
Jon Mitchell
A. I had to double-check my references before venturing to answer the simple
question, "what is Dynamic HTML?" That's because Dynamic HTML (DHTML) is not actually a scripting or markup language. DHTML is the concept of using a browser scripting language to animate, stack and format HTML content already loaded on the screen. Along with existing standards such as Cascading Style Sheets, DHTML allows the developer to control every aspect of a page: behavior, fonts, page formatting and layout.
The benefit DHTML provides is an overall interactive enhancement to an otherwise static Web browser experience. With DHTML we can create dynamic Web site graphical user interfaces (GUIs) that behave and feel like native operating system GUIs without refreshing the browser to the server for a state change. And there's no downloading additional applets, controls, or software plug-ins. Developers commonly use DHTML pop-out menus to reduce the number of clicks necessary for users to access information.
I hesitate to say that DHTML is widely used in Web sites today, but it is common to see it implemented. From the surface it's hard to understand why all Web sites aren't loaded with DHTML. The single biggest problem with serving up DHTML resides in the Document Object Model (DOM). DHTML is an object-oriented creation and its underlying skeletal structure is the DOM.
The DOM defines how a Web page is broken down into building-block objects that a scripting language can manipulate and interact with.
Unfortunately for developers, when DHTML was introduced there were no DOM standards, so Microsoft and Netscape naturally adopted different DOMs for their browsers. In order to create cross-platform DHTML, developers have to painstakingly branch (or write two separate versions of) DHTML code in order for their code to work across the two Web browsers. What's even more frustrating is DHTML code that functions erratically across multiple operating systems under the same browser and version number.
The World Wide Web Consortium ( http://www.w3c.org) has published its first official release of recommendations for DOM standards, DOM 1. Browser makers must adhere to DOM standards and delinquent DOMs must be eliminated in order for developers to write true cross-platform applications, for businesses to reduce the time and costs of Web site development, and for users to view Web sites that consistently present information correctly.
Every DHTML developer will appreciate having O'Reilly's Dynamic HTML A Definitive Reference handy. For more information on DHTML online, try Builder.com's DHTML tips ( http://www.builder.com/Authoring/Dhtml/ ), Web Review's DHTML introduction ( webreview.com/wr/pub/1999/06/18/feature/index.html), and Dan Steinman's DHTML tutorials and components (http://www.dansteinman.com/dynduo/). If you1d like to learn about DOM standards in more depth, The Web Standards Project (http://www.webstandards.org) is a good resource.
Kevin Jenkins
Founder, CEO
Thinksource Inc.
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