DHTML is the merging of HTML and JavaScript.
With DHTML we can alter the HTML page while it is
being displayed, and provide animated content to the viewer.

introduction to DHTML at:
http://www.webdevelopersjournal.com

Examples
/dhtml_examples.asp
follow these examples, try it out...

Re-Create the Moveable Table
dynamic.html
wObjects/test.htm

...then move on to Assignment 5
dhtml_layers.html