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As you become more experienced at programming real-world Web sites that use Active Server Pages, you start to notice that various applications seem to require a common set of features. For example, mass market, commercial sites tend to derive revenue from advertising for other third parties. If you work on these types of sites, many times you'll find yourself building functionality that shows different ads at different times. Also, it's common that most sites want to keep track of the number of times that a page is used or to offer "what do you think" voting capabilities that allow users to report their preferences on certain topics and products. Granted you could build these features from scratch using VBScript and ASP. The technology is that powerful. However, implementing common features repeatedly gets old, fast.
Microsoft understands that most Web sites require certain features and functions repeatedly. The company has responded accordingly by creating a set of ActiveX components, which you can use to implement these often-needed functions. These components are called Installable Components for Internet Information Server. These ActiveX components ship free with Internet Information Server.