The world is a complex and changeable place. Things move. Time passes. And perhaps you wish to represent such volatility in your online resource.

Advanced Animation
Simple GIF animation is useful for illustrating repetitive motion. Advanced animation technologies let you depict more complex movements and transformations, and to synchronize the changing image with sounds. Advanced animation can also interactivity: elements of the animation might respond to user events, such as mouse clicks or text input; users might be able to control how the animation progresses; or you might use the animation to simulate a physical process.

Consult a graphic designer about advanced animation technologies like Shockwave" or Flash" animation by Macromedia. Users generally need special browser plug-ins to view such animation properly. If you choose to include such elements in your resource, you should provide links to the appropriate plug-ins.

Video
Sometimes what you need to show has to have a real-world quality that only video can provide. The Web can now display video is several formats, although file sizes and processing requirements limit the degree to which some users may be able to access video files. Accordingly, you should make video elements optional and be sure that you really are showing something in the video that a static graphic or other animation format might not convey equally well.

Video formats include:

• QuickTime" video, developed by Apple Computer, which is popular because players are available for virtually every platform.
• MPEG video, which offers tremendous compression ratios -- but is not as common.
• Streaming video formats such as RealVideo from RealNetworks, which work much like streaming audio, allowing the video to play as it arrives from the server.

Initially, both MPEG and QuickTime technologies required the user to download the entire video file before it begins to play. Both MPEG and QuickTime are under continuous development. Streaming video players that support MPEG technology, such as Microsoft's Windows Media Player, are already available, and QuickTime is also moving toward streaming.

Virtual Reality
And sometimes nothing gets your point across as well as virtual exploration of a space. Using a format such as QuickTime VR or IPIX, users might be able to wander about a museum, the ruins of an ancient civilization, a distant mountain peak, or underwater.

Standards for the Web also include a language for constructing and presenting more complex, immersive environment online -- VRML ("Virtual Reality Modeling Language"). VRML worlds require plugins to view properly. Also, VRML worlds can be bulky -- something to consider if your target users typically labor with slow Internet connections.

For more information about VRML and virtual reality modeling on the Web , visit:

• The VRML Consortium (They wrote the spec)
• The VRML Repository at San Diego Supercomputer Center
• VRMLWorks