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Part V: Scripting, Dynamic HTML, and Dyn... > Using FrontPage's Dynamic Styles and...

Chapter 24. Using FrontPage's Dynamic Styles and Effects

In this chapter

Using the DHTML Effects Tools


Designers Corner

You saw in the previous chapter how scripting can be used to provide on-the-fly changes to text styles and page appearance. This is, of course, an example of Dynamic HTML (DHTML), an important software technology—or collection of technologies—that helps you create pages whose structure, content, or appearance can be changed in response to user input.

Until DHTML, most such changes had to be made with custom programming at the server side of the web connection, so that any change in a page required that an entire new version of the page be downloaded to the user's machine (the client). If there were many such changes, the load on the server became very high and response times suffered. However, all the changes are made on the client machine with DHTML (assuming a DHTML-capable browser is receiving the pages). Because there is no server round-trip time for page modification, the user gets faster results and the server breathes a sigh of relief. The end result, from the user's point of view, is that the page changes its appearance and its behavior in response to his use of the mouse or keyboard. This enhanced capability to respond to users' input is the reason for characterizing this development of HTML as dynamic.

The specification for this extension of HTML has been laid down by the Word Wide Web Consortium (W3C), the organization responsible for standardizing the HTML language. This specification is referred to formally as the Document Object Model (DOM). This originated with Netscape in the first version of JavaScript used in Navigator 2.0; in 1997 it was extended by Microsoft and SoftQuad in anticipation of W3C's recommendation of a DOM standard. This recommendation is now in force; you can examine it at http://www.w3.org/TR/REC-DOM-Level-1/.

Netscape and Microsoft have both tended to take their own approaches to DHTML, which has unfortunately led to browser compatibility problems. The behavior of Microsoft's IE4 and IE5 browsers is fairly compliant with the DOM specification, while Navigator 4 tends to use more proprietary methods of doing things. These methods, such as JavaScript style sheets, layering, and font technology, are not supported by IE 4 and IE5. It would be much preferable if both browsers rendered Web page content in exactly the same way, but so far it hasn't happened.


The reference page for Netscape's version of DHTML is found at http://developer.netscape.com/library/documentation/communicator/dynhtml/.

The reference page for Microsoft's version of DHTML is found at Netscape's http://www.microsoft.com/workshop/author/default.asp.

FrontPage 2000 also uses Microsoft's DHTML approach. That being the case, you will notice that the DHTML effects produced by FrontPage 2000 work best (or only) in IE 4 and later. If you use these effects in a public-access Web site, where you can't control what browser is in use (as you often can with an intranet) you should create alternate Web pages for people who are not using IE4/5, and direct such people to those pages. Creating such pages is obviously more work, so you may want to think hard before liberally salting your Web site with FrontPage's DHTML effects.

The W3C Document Object Model

The W3C has this to say about the model and about DHTML:

"The Document Object Model is a platform- and language-neutral interface that will allow programs and scripts to dynamically access and update the content, structure and style of documents. The document can be further processed and the results of that processing can be incorporated back into the presented page. [The term] 'Dynamic HTML' is a term used by some vendors to describe the combination of HTML, style sheets and scripts that allows documents to be animated. W3C has received several submissions from members companies on the way in which the object model of HTML documents should be exposed to scripts. These submissions do not propose any new HTML tags or style sheet technology. The W3C DOM WG is working hard to make sure interoperable and scripting-language neutral solutions are agreed upon."

As mentioned earlier, you can get up-to-date information on the DOM spec at http://www.w3.org/TR/REC-DOM-Level-1/. The general W3C site for DOM is at http://www.w3.org/DOM/.

The best way to understand FrontPage 2000's implementation of DHTML is to actually use it. The remainder of this chapter examines the tools that FrontPage 2000 offers to create interesting DHTML effects. Keep in mind, however, that overuse of dynamic elements on a page can be irritating and distracting. DHTML effects are a means to an end, not an end in themselves. There should be a constructive purpose for every piece of DHTML included in your web.


Remember that FrontPage gives you control over browser compatibility settings so that you can disable FrontPage components that won't work with a particular browser version. These adjustments for browser types are examined in Chapter 2, "The FrontPage Environment."



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