The earliest non-static Web sites were built using the Common Gateway Interface (CGI). CGI processed requests directly, issuing responses by firing up a custom process to handle incoming HTTP requests. The next step in improving Web site performance was to process HTTP requests through DLLs, which are much less expensive than loading new processes. On the Windows platform, these are known as ISAPI DLLs which are customized to spit out HTML specific to the task.
ASP was introduced because the process of writing ISAPI DLLs was burdensome. Think of classic ASP as one big ISAPI DLL that Microsoft has already written for you. Classic ASP accepts HTTP requests and posts back responses. You control the content coming from ASP using ASP code. ASP parses files with .ASP extensions and does its best to emit the right kind of HTML. Classic ASP pages include both raw HTML and script blocks. Accessing the HTTP requests and responses at runtime is possible because the requests and responses are wrapped in well-established objects you can access from the script blocks.
Classic ASP goes a long way towards simplifying Web programming. It's often much easier to write some HTML and mingle it with some script than it is to write a new DLL from scratch. But classic ASP is not without its issues. First, ASP code is often without structure. It's very much like the early days of BASIC programming where you could get something done quickly, but the resulting code was often too difficult to follow.
ASP.NET is the evolution of ASP. For example, you still have the same intrinsic objects in ASP.NET and you can add scripting wherever you want on the page. In fact, most ASP pages can be run as ASP.NET pages with no problem.
But ASP.NET brings a lot of new stuff to the table. First, ASP.NET supports every .NET-compliant language. No longer are you confined to using JScript® or VBScript on your Web pages. ASP.NET lets you write the executable parts of your pages in C# or Visual Basic (or COBOL). Second, ASP.NET is compiled into assemblies just like the other languages in .NET. This provides both enhanced performance and security benefits.

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There are many advantages of using Java Server pages (JSP) over ASP, SSI, JavaScript, HTML. We shall look at some of them in detail.

• vs. Active Server Pages (ASP). ASP is a similar technology from Microsoft. The advantages of JSP are twofold. First, the dynamic part is written in Java, not Visual Basic or other MS-specific language, so it is more powerful and easier to use. Second, it is portable to other operating systems and non-Microsoft Web servers.
• vs. Pure Servlets. JSP doesn't give you anything that you couldn't in principle do with a servlet. But it is more convenient to write (and to modify!) regular HTML than to have a zillion println statements that generate the HTML. Plus, by separating the look from the content you can put different people on different tasks: your Web page design experts can build the HTML, leaving places for your servlet programmers to insert the dynamic content.
• vs. Server-Side Includes (SSI). SSI is a widely-supported technology for including externally-defined pieces into a static Web page. JSP is better because it lets you use servlets instead of a separate program to generate that dynamic part. Besides, SSI is really only intended for simple inclusions, not for "real" programs that use form data, make database connections, and the like.
• vs. JavaScript. JavaScript can generate HTML dynamically on the client. This is a useful capability, but only handles situations where the dynamic information is based on the client's environment. With the exception of cookies, HTTP and form submission data is not available to JavaScript. And, since it runs on the client, JavaScript can't access server-side resources like databases, catalogs, pricing information, and the like.
• vs. Static HTML. Regular HTML, of course, cannot contain dynamic information. JSP is so easy and convenient that it is quite feasible to augment HTML pages that only benefit marginally by the insertion of small amounts of dynamic data. Previously, the cost of using dynamic data would preclude its use in all but the most valuable instances.

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