Java and JavaScript

A significant advance in Web technology was Sun Microsystems' Java platform. It enables web pages to embed small programs (called applets) directly into the view. These applets run on the end-user's computer, providing a richer user interface than simple web pages. Java client-side applets never gained the popularity that Sun had hoped for a variety of reasons, including lack of integration with other content (applets were confined to small boxes within the rendered page) and the fact that many computers at the time were supplied to end users without a suitably installed Java Virtual Machine, and so required a download by the user before applets would appear. Adobe Flash now performs many of the functions that were originally envisioned for Java applets, including the playing of video content, animation, and some rich UI features. Java itself has become more widely used as a platform and language for server-side and other programming.
JavaScript, on the other hand, is a scripting language that was initially developed for use within web pages. The standardized version is ECMAScript. While its name is similar to Java, JavaScript was developed by Netscape and it has almost nothing to do with Java, although, like Java, its syntax is derived from the C programming language. In conjunction with a web page's Document Object Model, JavaScript has become a much more powerful technology than its creators originally envisioned. The manipulation of a page's Document Object Model after the page is delivered to the client has been called Dynamic HTML (DHTML), to emphasize a shift away from static HTML displays.
In simple cases, all the optional information and actions available on a JavaScript-enhanced web page will have been downloaded when the page was first delivered. Ajax ("Asynchronous JavaScript And XML") is a JavaScript-based technology that provides a method whereby parts within a web page may be updated, using new information obtained over the network at a later time in response to user actions. This allows the page to be more responsive, interactive and interesting, without the user having to wait for whole-page reloads. Ajax is seen as an important aspect of what is being called Web 2.0. Examples of Ajax techniques currently in use can be seen in Gmail, Google Maps, and other dynamic web applications.