 The file extension tells to the browser how to deal with it. Image formats that are supported by practically all browsers are Graphics Interchange Format (GIF) and Joint Picture Encoding Group (JPEG). Also video and audio files can be inserted in the same manner. Data Communications Many comprehensive books are available about HTML for a reader who wants to see what it provides in detail and probably design her own home page. HTML, HTTP, and browsers are continuously being developed and new features implemented. However, Web page designers should take care that attached video and audio files are in formats that most browsers support. They should also note that all users might not have the latest browser version. A user probably will not want to visit a Web page again if it merely gives blank video windows and error messages. Another thing that is very frustrating for Web users is that the informa- tion provided by WWW is often out of date. It would probably be better for the image of a company to provide no information rather than the wrong information via the Web. 6.6.11.4 Java HTML is designed to show static pages on the screen of the browser. Every change on screen requires a client-server interaction, which may slow the response. In many cases, the response could be given locally by the browser if software that produces it were available. Examples are background music played locally while surfing, a game loaded to the browser, clicking a cat to make it meow, and complex forms (such as spreadsheets). These can be implemented with the language called Java. An interactive Web page can point to a small Java program, called an applet, which the client downloads and runs locally. Now only information that cannot be produced locally needs to be transmitted and this approach may improve the performance of Web service. In particular when a user has wireless access to the Internet, it is essential to avoid unnecessary transmis- sion and instead perform processing locally. Mobile terminals supporting Java are an import