The Motive Web Design Glossary
dynamic HTML (dHTML)
Dynamic HTML is an extension to the standard HTML language introduced by version 4+ browsers (Netscape Navigator and Internet Explorer). "Dynamic" makes reference to changing the webpage display in response to user interaction.
Referencing page elements
Dynamic HTML allows the elements of a page to be referenced individually and by extension modified. A common application of this principle is the navigation roll-over. One image is swapped for another when the user passes their mouse over it.
Layers
Prior to Dyamic HTML, webpage layout adhered to principle not dissimilar to metal typesetting. Each element on the page (image, block of text, etc.) was very much a 'physical' element, placed next to but not on top of it's neighbour. If, through some authoring quirk, two elements were located in the same space, one would typically displace the other.
Dynamic HTML introduced the ability to build an HTML document from a number of individual (stackable) layers. Elements can therefore overlap one another.
Layers are used in practise to create drop-down menus that float over the page content. The menu toggles between visible and invisible as the user moves their mouse over and off the associated hotspot.
Client-side scripting
To take advantage of Dynamic HTML also requires the use of a scripting language that can run inside of the browser; such as JavaScript.
Many applications of DHTML also rely upon stylesheets, changing the class of an object as the result of user interaction to modify it's display -- changing its size, colour, typeface etc.
browser, HTML, JavaScript, stylesheets.
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