Java

Java is a programming language that can be used for just about anything. It is free and it runs on any operating system you are likely to find, including Windows, Macintosh, and Linux -- also PDAs, cell phones and any device that has something called a Java Virtual Machine on it. You can make webpages do interesting things by using Java Applets. In general, I don't think it is a good idea to use them very often because the visitor to your webpage has to have a plugin called the Java Runtime Environment (JRE) installed or they won't be able to see the applet. Java applets can't be viewed without the JRE installed.