Web Design in a Nutshell, 2nd Edition

Chapter 29. Introduction to DHTML

HTML is based on thinking of a web page like a printed page: a document that is rendered once and that is static once rendered. The idea behind Dynamic HTML (DHTML), however, is to make every element of a page interactively controllable, before, during, and after the page is rendered. This means you can make things move, appear and disappear, overlap, change styles, and interact with the user to your heart’s content. Through DHTML, users get a more engaging and interactive web experience without constant calls to a web server or the overhead of loading new pages, plug-ins, or large applets.

DHTML is not a language itself, but rather a combination of:

• HTML 4.0 (or XHTML 1.0)

• JavaScript—the Web’s standard scripting language

• Cascading Style Sheets (CSS)—styles dictated outside a document’s content

• Document Object Model (DOM)—a means of accessing a document’s individual elements

Since the first edition of this book, Dynamic HTML has developed into a stable standard that is well supported by both Netscape 6 and Internet Explorer 5.5.

Netscape Navigator 4.0 and IE 4.0 supported earlier, proprietary versions of DHTML, and they differed greatly in their support for CSS and dynamically positioned elements. The differences between what these two browser versions called DHTML has created a million migraines among web developers. Accounting for the inconsistencies required creating two separate web pages or jumping through browser-detection hoops to give all ...