Defined as an art form

Dynamic HTML can be viewed as a mode of expression for communicating with people, like other visual art forms such as painting, dance, or the iconized, mouse-driven graphics of a computer's desktop.

Like plain HTML, Dynamic HTML appears in a web browser window. Unlike plain HTML, the possibility of images, icons and text moving and reacting to each other creates a new mode of communication that the user must learn to interact with. This kind of interaction is particularly important when browsers are run in full screen mode, such as at information kiosks or via Netscape's Netcaster. In those cases, the user's normal mode of interaction for navigation tasks (via browser toolbars and menus) is not available, and Dynamic HTML features must substitute. The user must learn that key elements of a Dynamic HTML page mean that certain effects will follow.

The ability to position HTML elements at exact locations on a page allows elements to overlap. HTML is normally strictly two-dimensional, but overlapping elements require some organization in the third dimension. However, browsers are not capable of full three-dimensional effects, and in any event all that is really required is a stacking order for overlapping elements. A stacking order merely says which item is on top or which other item. So a browser window that is 800 pixels by 600 pixels, with perhaps 6 or less items in its content laying on top of each other, is called two-and-a-half dimensional, or 2.5-D, since the third dimension is much smaller in size than the other two. Rather than overlapping items with a whole third coordinate, the stacked items are said to have a z-order. A z-order is a convention that orders overlapping items based on an arbitrary number that is assigned to each item by the script writer.

Dynamic HTML draws inspiration from several other well-established media. It is strong on animated presentation graphics and slide shows. It is also similar to video digital editing, in that it allows effects like panning, wipes, zooms and insets. Dynamic HTML also draws from the world of animation, as it allows crude but flexible animation features. Because HTML documents can be textual, Dynamic HTML also allows some unique tricks of its own—menu expansion is a simple example.

For good examples of the potential of dynamic HTML, see the following Web pages:

• Presentation. Use Navigator 4.0 to view this hype from Netscape:

  http://developer.netscape.com/devcon/jun97/key_1/directs.html

  
  
  
• Video editing. Use Internet Explorer 4.0 to view this simple page:

  http://www.microsoft.com/sitebuilder/columnists/samples/Scale2.htm

  
  
  
• Animation. Use Navigator 4.0 to interact with this winner of the Netscape 1997 Dynamic HTML contest:

  http://developer.netscape.com/devcon/jun97/contest/freefall/index.html

  
  
  
• Menu expansion. Use Internet Explorer 4.0 to navigate through this Microsoft documentation:

  http://www.microsoft.com/workshop/prog/ie4

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Dynamic HTML has its limitations as well. It may be a visual art form that can produce useful interrelationships between textual and iconic elements on a page, but because of these effects it is a poor vehicle for communication with disabled users. It is difficult to do drag-and-drop style operations, for example, if you are blind. It also isn't widely accessible outside the two major browsers. Therefore it is a less conservative approach than plain HTML.

© 1997 by Wrox Press. All rights reserved.