The introduction of Cascading Style Sheets ( CSS ) gave Web authors unprecedented control over the look of their Web pages. CSS allows authors to attach a style to Web pages that defines the presentation of content by modifying the style attributes of corresponding HTML elements.

Newer browser versions take CSS technology a step further, providing the ability to dynamically change any HTML attribute on any element at any time. This allows us to change colors, typefaces, spacing, indentation, position, and even the visibility of text dynamically.

Using simple scripts compatible with the ECMA 262 language specification, such as JScript and JavaScript, the style attributes for any HTML element can be modified in response to any document or user event, and the page will automatically reflow without reloading the page from the server.

You might expect that this new functionality requires us to learn a new set of HTML tags. Fortunately, dynamic styles have been designed to require no new HTML.