A regular website comprises a set of related HTML pages and files hosted on a computer running a web server. A web server is software that serves web pages in response to requests from web browsers. A page request is generated when a user clicks a link on a web page, chooses a bookmark in a browser, or enters a URL in a browser’s Address text box and clicks Go. The final content of a regular web page is determined by the page designer and doesn’t change when the page is requested. Every line of the page’s HTML code is written by the designer before the page is placed on the server. Because the HTML doesn’t change once it’s on the server, this kind of page is called a static page. Note: Strictly speaking, a “static” page may not be static at all. For example, a rollover image or a Flash movie can make a static page come alive. However, this help system refers to a page as static if it is sent to the browser without modifications. When the web server receives a request for a static page, the server reads the request, finds the page, and sends it to the requesting browser, as shown in the following figure: In the case of web applications, certain lines of code are undetermined when the user requests the page. These lines must be determined by some mechanism before the page can be sent to the browser. The mechanism is discussed in the following section.
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