The traditional method of laying out web pages, HTML, is static. There are two ways of delivering content dynamically:

Server-side

A web server, running special software, constructs an HTML page 'on the fly', according to the user's request and possibly other variables, such as time or stock levels.

Client-side

Client-side scripting works at the user's browser, and therefore should not be used for "mission critical" work, where the user's capabilities are not known ?¢‚Ǩ‚Äú it is more suited to adding decoration and other ephemeral content. It is most often achieved through JavaScript.