Web pages are documents which form the building blocks of web sites and, in a wider context, the World Wide Web (or intranets). They are formatted using HTML (Hypertext Markup Language). Web pages can include text, images, audio, video, animation, links and forms. The capabilities of web pages can be further extended by the use of JavaScript (program code embedded in the HTML), Java applets (add-on programs) and plug-ins, such as Flash. Web pages can be created in advance of their use or generated on-the-fly by computer programs residing on the web server (the computer that hosts the website).