There are two places where web content can be dynamic for the user. The web server can insert HTML code into your page before it gets to the user's web browser, or you can send the instructions to the web browser for it to "figure out." There are a smaller number of options available to you for client-side development. JavaScript is, by far, the most widely used for manipulating HTML files and text. Going one step beyond HTML, web browsers also have plug-ins that allow us to see or hear "rich media" file formats like video, animation, and sounds, and even allow us to play games.

An example of a client-side instruction in JavaScript would be a simple date stamp. Inside your HTML file you place a JavaScript instruction that tells the web browser to "insert the date" here. This differs from a server-side instruction in that the web server will insert the date before the browser gets the file, meaning that the browser needs to show only the HTML.

We mentioned "rich media" files earlier — these are files that use browser plug-ins to display in the web browser. These are formats like Flash, QuickTime, Java Applets, etc. Many of these file formats can also be dynamic; however, the plug-ins are doing all of the work. Keep in mind, files that need browser plug-ins are still considered client-side files because the dynamic nature of the files is still being "figured out" on the user's computer, not on the web server.

Learn more about rich media on our What Is Rich Media? page.

Learn more about JavaScript on our What Is JavaScript? page.