by John December

What is Dynamic HTML?

Dynamic HTML (DHTML) is a name for a set of technologies that Web developers can use to create Web pages that update themselves on the fly. In a Web page implemented in DHTML, fonts, positions of elements, graphics might change as you look at it in a browser. Dynamic HTML makes your Web documents more interactive.

Just as in "regular" HTML, when a user downloads a page written in DHTML, the content is stored on the user's computer for viewing in the browser. In DHTML, this content might also contain instructions for how changes should take place in the presentation of the page. Dynamic HTML therefore happens on the client-side. It doesn't involve reconnecting to the server for more information.

Dynamic HTML is used in conjunction with Cascading Style Sheets (CSS). Using coordinate positioning available in CSS, a Web developer can place HTML elements in specific locations on a page. The HTML elements positioned this way can move according to a script (written in, for example, ActiveX using VBScript; or JavaScript) as the user views the page. This positioning can occur not only on the X-Y (flat plane) of the Web page, but in the Z direction, giving the illusion of depth or the stacking of one element on top of another.

There are differences in how the major players--Microsoft and Netscape--implement DHTML. Netscape had proposed a new proprietary element called LAYER to deal with Z-positioning (the LAYER element doesn't seem like it will be used widely). Microsoft agrees to the non-proprietary position of the W3C.

Dynamic HTML relates to the W3C's broader efforts to create an interface called the Document Object Model (DOM). The aim of DOM is to allow programmers to dynamically update the content, structure, and style of documents.

What is the Big Deal About Dynamic HTML?

The promise of DHTML is dynamic interaction between the user and a Web page. This is the promise of Java, but Web pages using DHTML techniques are less memory-intensive and faster than what current Java implementations of the same thing. This dynamism can give the user a richer experience with pages--allowing, for example, visual changes in the Web page to take place as result of user's mouse position. Creatively used, this could alleviate the need for a user to click the mouse button in order to indicate a choice. The potential is Web pages that more seamlessly invite and support user interaction.

Who is Using Dynamic HTML?

Hotwired announced the re-design of its Web site using DHTML in July 1997. The hideous color combinations and cluttered and akward visual design of this site isn't the fault of DHTML, however. Hotwired and its paper-based counterpart, Wired magazine, have been consistently ugly for years. What is interesting is that the Hotwired site does demonstrate features of DHTML. Awkwardly. But at least this was the first major site to do so.

My opinion of Dynamic HTML?

There's much potential in Cascading Style Sheets to bring visual discipline and consistency to Web sites. Used well, DHTML can be a formidable and elegant way to bring interactivity to a Web page.

Used as just one more method to create incomprehensible "slabs" of graphics embedded within frames, JavaScript, and other non-sense, DHTML is nothing more than a buzzword for the latest kind of posturing "coolness" that detracts from the value of most Web content.

I think DHTML is a technology to invest in, as long as you develop the meaning-making skills to use it well.

Information Sources for Dynamic HTML

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