Dynamic HTML

DHTML allows scripting languages to change variables in a web page's definition language, which in turn affects the look and function of otherwise "static" HTML page content, after the page has been fully loaded and during the viewing process. Thus the dynamic characteristic of DHTML is the way it functions while a page is viewed, not in its ability to generate a unique page with each page load.
Dynamic HTML or DHTML, is a collection of technologies used together to create interactive and animated web sites by using a combination of a HTML and CSS or JavaScript.
DHTML allows authors to add effects to their pages that are otherwise difficult to achieve. For example, DHTML allows the page author to:
Animate text and images in their document, independently moving each element from any starting point to any ending point, following a predetermined path or one chosen by the user.
Embed a ticker that automatically refreshes its content with the latest news, stock quotes, or other data.
Use a form to capture user input, and then process and respond to that data without having to send data back to the server.
Include rollover buttons or drop-down menus.

Dynamic HTML Tutorial
CSS
JavaScript