Of the 38 million Web sites surveyed in March, 58% were running on Apache - 4.2% down on February; and 29% were using Microsoft's Internet Information Services (IIS) servers - up 4.9% on the previous month.
Netcraft said part of the increase is due to domain name registrars Register.com and Network Solutions switching their domain parking facilities to Microsoft servers from Unix.
A domain park is where Web site name redirection takes place when a company has bought two domains but only uses one of them. This means that a user typing in www.domainname.co.uk would automatically be sent to www.domainname.com.
Once these "dead" sites have been filtered out of the survey's results, the increase is less marked, with Microsoft gaining by 0.7% and Apache, which mainly runs on Unix and Linux, falling by 0.8%.
Gary Barnett, a principal analyst at Ovum, said he believes Microsoft will gain ground as more smaller companies realise that their broadband links allow them to host their own Web sites. "Because IIS comes with Windows, it is no more expensive than Apache but has the advantage of sharing a common console with other Windows servers," he said. "These organisations would not be willing to pay the price for deploying an unfamiliar operating system."
Although Apache has a Windows version, the company openly admits that it is less stable than its Unix servers.
- Microsoft made something of a faux pas when it launched its anti-Unix Web site at www.wehavethewayout.com/ using Apache on Unix. After realising that its decision to use the open source platform could undermine the site's message, the company switched to IIS last week. The site then disappeared for two days due to a technical glitch.