Web sites that provide its visitors the ability to modify content based on their input are dynamic Web sites. You would have seen several examples of such Web sites on the Internet. Online shopping stores, search engines, email, chat and community portals, etc. are all examples or dynamic Web sites that allow you to save your profiles, customize the appearance of your account, alter default settings based on your preferences and a lot more.

It is not possible with HTML alone to develop a dynamic Web site. Dynamic Web sites utilize databases and other mechanisms that enable them to identify their visitors, present them with customized greeting messages, save their preferences and restructure their content according to user input. The term “server-side technology” is something that you will get to hear a lot in the Web development community. It is this mechanism that adds the dynamism to the dynamic Web sites.

Server-side technologies add an extra layer to the static Web page serving process that we saw earlier in the previous diagram. This extra layer enables the Web server to generate HTML on the fly. Hence if there are special instructions (server-side technology code) in the Web pages, the Web server (before serving pages) will first interpret them, generate the appropriate HTML and then send the response to the Web browser. The following diagram shows this and the instructions below explain the process.

1. 
   

   The Web browser sends a request for a particular Web page of a Web site to the Web server hosting that site.

   
   


2. 
   

   The Web server searches for the page in directory containing Web pages for the Web site.

   
   


3. 
   

   On finding the requested page, the Web server collects the content (code + HTML) of the Web page.

   
   


4. 
   

   The Web server then parses the content to produce HTML.

   
   


5. 
   

   The HTML stream is sent back to the requesting browser which then parses it to develop the visual presentation of the page.

   
   

Figure 2: Shows the serving process for dynamic Web sites.

There are several server-side technologies that exist today. ASP, PHP, JSP, CGI, Cold Fusion are amongst the popular ones