CSS defines how particular elements within the document are to be rendered. The object model for manipulating the properties of the style sheet is based on the CSS recommendation. When an attribute or rule is modified through script, the static style sheet is updated and the page is immediately updated.
This dynamic style model is different from the JASS model supported by Netscape Navigator 4.0. JASS is a procedural model for defining a style sheet for the document at parse time rather than a programming model for manipulating a document's style. For example, JASS can be used to write conditional code that applies a different style sheet depending on the size of the screen during the loading of the document. JASS can't be used to change the style of an element in response to an event without reloading or requesting a new page from the server.
In Microsoft Internet Explorer 4.0, dynamic styles are not a procedural style sheet language, but they can accomplish all aspects of JASS and much more. Rather than define an alternative style sheet language, dynamic styles in Internet Explorer modify the document's CSS-defined style sheet by allowing you to define inline style properties on every element, enable and disable all global and linked style sheets, and add rules to and changes rules on an existing style sheet.