In the case of web applications, certain lines of code are undetermined 

when the visitor 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.

Processing dynamic pages

When a web server receives a request for a static web page, the server sends 

the page directly to the requesting browser. When the web server receives a 

request for a dynamic page, however, it reacts differently: It passes the page 

to a special piece of software responsible for finishing the page. This special 

software is called an application server. 

The application server reads the code on the page, finishes the page 

according to the instructions in the code, and then removes the code from 

the page. The result is a static page that the application server passes back 

to the web server, which then sends the page to the requesting browser. All 

the browser gets when the page arrives is pure HTML. Here's a view of the 

process:

Web browser

Step 1   Web 

browser requests 

dynamic page.

Request

Response

Step 5   Web 

server sends 

finished page to 

requesting browser

WEB SERVER

Step 2   

Web server 

finds page 

and passes it