Since the dawn of the Web era, one technology has steadfastly dominated as the world's most popular Web server. That technology is the open-source Apache Web Server, commonly referred to simply as "Apache."

Internet research and security services firm Netcraft is now reporting that across the nearly 717 million Websites it has surveyed this month, Apache serves 46.96 percent of them. That is the first time that Apache's share has fallen below 50 percent since December of 2009. At its height—in November of 2005—Apache held a 71 percent market share.

At first glance, I personally would have thought that Apache's numbers were declining against open-source competitor nginx, which has steadily been winning praise and converts in recent years. Looking at the numbers provided by Netcraft, that's not the case. Apache this month is losing share not to nginx, but rather to Microsoft Internet Information Server (IIS).

No that's not a typo (yes I double-checked). From July to August, Microsoft gained 3.10 percent (ngnx gained 0.96 percent), ostensibly taking some share from Apache. While Microsoft is gaining, its total Web server market share for the month of August currently stands at 22.75 percent, so it's still less than half the market that Apache commands.

Perhaps even more surprising is that Apache's decline and Microsoft's rise are due to a single hosting company. According to Netcraft, hosting vendor GoDaddy recently moved 25 million sites from Apache on Linux to Microsoft's IIS 7.5

Active Sites

Going a level deeper, Netcraft also has a methodology for determining the current state of active sites on the Internet. These are sites that by definition are active (as opposed to just being parked pages for domains) and in use. Microsoft IIS is still gaining by that measure, though not nearly as much.

So far in August, Microsoft IIS has gained 0.84 percent, to hold an 11.78 share of all active sites. In contrast, Apache lost 0.92 percent and still holds an industry-leading 53.62 percent active site share.

From a personal perspective, I've always been amazed at the longevity of Apache's success. In many respects, it is the most successful and widely deployed open-source technology today. For various reasons, I had at one time thought that Apache would fall by the wayside, much like Netscape (which once dominated the browser landscape) fell in the late 1990s to Microsoft's Internet Explorer (IE) browser. Thankfully, that never happened to Apache.

It is my belief that the fact that Apache is open source and free is key to its success (Netscape was free, but not initially open source until the Mozilla era). It's also critical in my view to link Apache's dominance with the open-source Linux operating system servers on which Apache typically runs (yes, I know Apache can run on a Windows Server too). Apache is part of every major Linux distribution, and when a new Linux server is deployed, Apache usually is as well.

Will Microsoft IIS ever overtake Apache, as IE overtook Netscape? That seems unlikely, even though in any given month (this month is a great example), IIS can take some share. The reality is that Apache simply has a massive existing entrenched user base of at least 364 million sites today. While some of those sites will move, most of them likely work well enough and aren't going to be moving to another technology anytime soon.

Sean Michael Kerner is a senior editor at eWEEK and InternetNews.com. Follow him on Twitter @TechJournalist.