This version of IIS was pretty basic, and changing advanced settings usually involved messing around with the Windows registry. By contrast, version 4.0 of IIS saw a radical change to the application. IIS 4.0 sported a completely new user interface, a host of new features, and improved reliability. It is a useful web server to run if your system resources are limited, and even has support for Active Server Pages. It supports a limited number of simultaneous connections.
Performance is poor.
There are many more features, particularly in the areas of security and access control. The web server runs as a service, so nobody needs to be logged into the machine in order for the web services to be accessed. The full version of IIS requires installation on Windows NT Server. This version supports an unlimited number of simultaneous network connections. Hosting on the other operating systems is, however, useful for development purposes.