Have you ever wondered just how many companies are running Microsoft IIS? Netcraft, a UK-based Internet company, has published many reports throughout the years showing the market dominance of the Apache Software Foundation's Apache HTTP Server. Netcraft's recent reports show a 62 percent market share for the Apache HTTP Server compared with IIS's 27 percent market share ( http://www.netcraft.com/survey ). For the past 5 years, I've accepted Netcraft's reports and watched as IIS slowly gained market share.

This month, Port80 Software, a San Diego-based software company, electronically surveyed the Fortune 1000 to find out exactly which companies are running IIS and which aren't. Port80 Software's online tool queries the HTTP request header returned by a Web server to determine which Web server software is running. The server header, which is part of the HTTP request header, is an optional header that's usually used to identify the Web server software's vendor and version.

Port80 Software's survey returned some interesting results. You can read more about Port80 Software's survey of the top 1000 corporations and run its tool at http://www.port80software.com/servermask/top1000webservers . Contrary to Netcraft's results, Port80 Software's Fortune 1000 survey shows a 54.1 percent market share for IIS, 21 percent share for Sun Microsystems' Netscape Enterprise Server, 17.6 percent for the Apache HTTP Server, and 7.3 percent for all others.

Several factors could be causing vastly different results between the Netcraft and Port80 Software surveys, yet both results have validity. Consider the fact that that Netcraft's results measure all domains on the Internet (approximately 33 million) and Port80 Software's results measure only the public Web sites of the top 1000 companies. A plethora of servers run Sun and Apache that are hosting hundreds, if not thousands, of Web sites on single computers. IIS has been historically bad at hosting large numbers of sites on the same box. In fact, you simply can't host enormous numbers of sites on one Internet Information Services (IIS) 5.0 or earlier server in a farm (whether it's load balanced or not), which explains Netcraft's results that single machines (Sun and Apache) are hosting thousands of static Web sites.

When you visit the Netcraft site to review its survey results, also take note of its report about an IIS 5.0 Web server that went without a reboot for more than 2 years. The IIS server ( http://www.byteandswitch.com )has been running continuously since November 2000. The industry seems to have a negative perception of the stability of IIS. That perception certainly was valid with Internet Information Server (IIS) 4.0 and earlier, but not with IIS 5.0. In the hosting industry, Microsoft partners Interliant and divine each have sites that haven't been rebooted in more than a year. Microsoft also has run several of its sites for more than a year between reboots. Such facts will go a long way toward dispelling the myth of IIS instability.