JavaScript is a programming language that (almost) all web browsers understand. It's the main language used for client-side scripting: adding logic and commands into a web page to get it to do stuff.

It's used in other places (like server-side code, inside Flash movies etc.), but it started life as a lightweight script for the web. It's compact and fairly easy to learn, similar in style to other languages like C and PHP.

DHTML covers a range of techniques whereby you manipulate the HTML document, and HTML elements within the document, using client-side scripting (i.e. JavaScript).

DHTML lets you do pretty much anything you want to a web page, including moving stuff around, changing the way it looks, remove bits of the page and even add new ones.

In this section I'll introduce you to the basics of how to write JavaScript, and include some examples of what you can do with it to make your web pages and applications more powerful, easier and nicer to use.