HTML 4 For Dummies - Bonus Chapters

What's So Cool about DHTML?


For the moment, ignore the competing visions for DHTML and just try to get the basic concepts straight. This not only helps you understand what the fuss is all about, but it should also help you appreciate why DHTML really is pretty important, and what kind of impact DHTML could have on the Web in general, and maybe even on your own Web pages.

The essence of DHTML is this: Instead of transferring and creating static HTML-based documents on the client side of a Web connection, DHTML makes it possible to transfer a document description to the client side that can be changed in specific ways once it gets to the client, by activating associated scripts to rewrite the HTML and redisplay it (the Microsoft way) or by setting up different views of information on multiple layers in a document, and then switching between layers to change from one view to another (the Netscape way).

DHTML may not sound too exciting in the abstract, so to get a little more specific, we discuss what this can do for a Web page:

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  • DHTML creates terrific support for hierarchical menus, in which clicking a selection on one menu causes another submenu to pop up (in other words, this lets Web designers create a user interface that’s familiar to anyone who’s used a GUI application like MS Word, a Web browser, and so on).

  • The ability to change the page on the client side, in response to user selections (no matter how it’s handled), means that users can interact with Web documents much more quickly, because they don’t have to issue a request for a new page to the server across the Internet and wait for that page to arrive. DHTML enables Web page designers to package everything needed to support interactivity in a single document and send that document to users all at once, instead of a little bit at a time. That helps explain why some experts say that DHTML may replace the current Web site architecture, which consists of lots of simple, static HTML documents, with many fewer, but much more complex, dynamic HTML documents.

  • Because HTML supports style sheets (CSS1 and CSS2), and DHTML can operate on style sheets as well as HTML documents, page designers can even change styles dynamically. Font selections, sizes, and text color can all change in response to user actions on a Web page. For example, the contents of a Web site map could be presented in 4 or 5 point black type to allow as much information as possible to fit on a single screen, but whichever item the user selects for examination could be presented in more readable 8 or 9 point type, with multiple colors. DHTML can even reflow the other text around whatever the new focus might be to make it appear as the current “center of attention.” The possibilities for this kind of dynamic handling for whatever becomes the user’s focus in a document are limitless and magical.

  • Microsoft announced in 1996 that it would switch its Windows Help environment from a proprietary implementation to HTML. Because of the need for access to help topic indexes, multiple displays, and precise positioning of elements on screen, DHTML is an ideal technology to use for building help systems. As an added bonus, such documents would work equally well from a CD-ROM, a hard disk, or across the Web.

We really could go on (and on and on) here, but we hope this gives you an idea of the extraordinary power and potential inherent in DHTML! In the sections that follow, we take a closer look at Microsoft’s and Netscape’ ideas on this fascinating subject, and then show you how the W3C is trying to create a standard out of these powerful, but incompatible, visions.

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