Active Server Pages (ASP) is Microsoft's server-side script engine for dynamically-generated web pages. It is marketed as an add-on to Internet Information Services (IIS).

Programming ASP websites is made easier by various built-in objects. Each object corresponds to a group of frequently-used functionality useful for creating dynamic web pages. In ASP 2.0 there are six such built-in objects: Application, ASPError, Request, Response, Server, and Session. Session, for example, is a cookie-based session object that maintains variables from page to page. Application Center Test is also available for load testing.Most ASP pages are written in VBScript, but any other Active Scripting engine can be selected instead by using the @Language directive or the <script language="language" runat="server"> syntax. JScript (Microsoft's implementation of ECMAScript) is the other language that is usually available. PerlScript (a derivative of Perl) and others are available as third-party installable Active Scripting engines."PWS is a smaller, but fully functional version of IIS. To run PWS, we need Windows 95 or later. InstantASP, ChiliASP are technologies that run ASP without Windows Operating System."There are large open source communities on the WWW, such as ASPNuke, which are producing ASP scripts, components and applications to be used for free under certain licence terms.

Microsoft Internet Information Services (IIS; sometimes, erroneously called Server or System) is a set of Internet-based services for servers using Microsoft Windows. It is the world's second most popular web server in terms of overall websites behind the Apache HTTP Server although the gap is decreasing according to Netcraft.The servers currently include FTP, SMTP, NNTP and HTTP/HTTPS.

History

IIS was initially released as an additional set of Internet based services for Windows NT 3.51. IIS 2.0 followed adding support for the Windows NT 4.0 operating system and IIS 3.0 introduced the Active Server Pages dynamic scripting environment.IIS 4.0 dropped support for the Gopher protocol and was bundled with Windows NT as a separate "Option Pack" CD-ROM.The current shipping version of IIS is 6.0 for Windows Server 2003 and IIS 5.1 for Windows XP Professional. IIS 5.1 for Windows XP is a restricted version of IIS that supports only 10 simultaneous connections and a single web site. IIS 6.0 added support for IPv6.Windows Vista will come preinstalled with IIS 7.0. It will not limit the number of connections allowed but will limit workloads based on the active concurrent requests, improving usability and performance in peer-to-peer scenarios.

The Apache HTTP Server is a web server for Unix-like systems, Microsoft Windows, Novell NetWare and other operating systems. Apache is notable for playing a key role in the initial growth of the World Wide Web.When first released, Apache was the only viable open source alternative to the Netscape Communications Corporation web server (currently known as Sun Java System Web Server). It has since evolved to rival other Unix-based web servers in terms of functionality and performance. Since April 1996 Apache has been the most popular HTTP server on the World Wide Web, serving as the de facto reference platform against which other web servers are designed and judged; as of January 2007 Apache served 60% of all websites.Apache continues to be the most popular web server in use.Apache is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation.  

from : en.wikipedia.org