Posted: July 19, 2004

This chart shows the development of some of the Document Object Models (DOMs) supported by Internet Explorer (IE). A DOM is an object-based API for reading and editing an HTML or XML Web document.

Since the introduction of IE 3.0 in 1996, IE has supported two programming languages for client-side HTML: VBScript (a derivative of Microsoft’s Visual Basic language) and JScript (Microsoft’s implementation of JavaScript).

The most basic DOM supported by IE is the IE 3.0 DOM, also known as the W3C Level 0 DOM. It provides basic access to the elements of an HTML page and limited support for modifying the page. For example, a developer can use the Level 0 DOM to write a mouseover trigger that changes the contents of an image when the user hovers the mouse over it.

In 1997, Microsoft extended the basic DOM with Dynamic HTML (DHTML), a more full-featured DOM that allows developers to build user interface elements such as drop-down menus. The DHTML DOM was never standardized by the W3C, but is still supported in current versions of IE.

As part of its standardization efforts, the W3C defined a Level 1 DOM which included the same functionality as DHTML but also incorporated features found in competing browsers, such as Netscape. Although IE 5 was partially compatible with the Level 1 DOM, Microsoft did not have a fully compatible browser until IE 6.0 in 2001.