Microsoft’s Internet Information Services (IIS) continues to narrow the gap with the open-source Apache Web server, with a survey firm suggesting that Redmond’s offering could surpass Apache as early as next year.

Microsoft, which added 2.6 million Web sites in the last month, grew to 36.2 percent of all active websites, according to figures released this week by UK-based research firm, Netcraft. Apache meanwhile lost nearly a million website names, as its share of active websites fell to 48.4 percent.

Apache now leads IIS, which is bundled with Windows Server, by 12.2 percent among active websites, a list which excludes registered domain names that are not yet in actual usage.

“But if Microsoft continues to gain share at its current pace, it could close the gap on Apache sometime in 2008,” said the Netcraft posting accompanying the survey results.

That’s a major turnaround in two years. Apache has led the Netcraft survey since its inception back in 1995. By November 2005 it was running 71 percent of all Web sites. That gave Apache a greater-than 50 percent lead over IIS’s 20.2 percent share, and caused commentators such as Oracle executive Larry Ellison to declare that IIS had been “wiped off the face of the earth” by Apache.

But Microsoft’s recent gains have been so fast that furious open-source proponents such as Bruce Perens claimed last year that Microsoft was paying large domain name resellers such as Go Daddy to “park” unused domain names in IIS rather than Apache.

Perens, who set up a website called OpenSourceParking.com for users to park their domain names on an Apache server to counter what he sees as Microsoft’s attempts to manipulate mindshare, conceded that Apache's market share is declining, although he attributed it to the growing popularity of other open-source Web servers such as lighttpd.

“Technology evolves,” Perens said in an email. But businesses that use IIS are bringing trouble upon themselves, he argues. “My own web server running Linux does not have a firewall, it’s been on the Net for 10 years and has never needed one. Try running any MS operating system naked on the Net that way.”

Chris Neppes, sales and marketing director for IIS add-on vendor, Port80 Software, says Netcraft’s list of active Web sites helps avoid “parked” domains, though he said the methodology is not as foolproof as Port80's own surveys, which include just Web sites of Fortune 1000 companies.

That data shows IIS in use at 55 percent of websites, versus Apache's 24.9 percent.

Only one Fortune 1000 firm today - Microsoft - is using IIS 7.0, which Microsoft is set to release next February as part of Windows Server 2008.

Neppes believes that IIS 7.0 will help Microsoft win more users at Apache’s expense. IIS has traditionally been harder to configure and tune than Apache, he said. Moreover, IIS’ kludgy ISAPI interface limited the ability for users to run third-party components compared to Apache, which has a thriving ecosystem of free open-source add-ons available to users.

Not only has ISAPI been updated, but IIS 7.0 is the first version to have an “extensibility model built into the core server,” Neppes said. “Every piece of the Web server can be flipped on or off. It’s now very granular, meaning you can turn off services you don't need to reduce the attack surface.”

Neppes doesn't expect IIS 7.0 uptake to be immediate. Past surveys by his firm show that the majority of Fortune 1000 firms don’t upgrade to the latest version of IIS until three years after its release.

For instance, data that Port80 plans to release later this month showed IIS 6.0, which shipped with Windows Server 2003, surpassing the 7-year-old IIS 5.0, which came with Windows 2000 and XP Pro, only this year.