The latest results seem to be showing that the traditional dominance of the open source web server Apache is being eaten away by Microsoft's improved server offerings.
This has led me to ask what the big ISPs are using for their own websites. And that's where Netcraft's genius What's That Site Running? tool comes into play.
I've ignored the fact that the big ISPs (and I've just used ISP Review's list of them) have many different hostnames (e.g. for customer webspace) and just looked at their main corporate sites.
ISP CUSTOMERS WEB SERVER OPERATING SYSTEMThe results tell us that, even though Microsoft's share of the overall web server market is increasing, that only Kingston are evidently using their software to host their website (there may be others within the 'unknown' group - who have chosen not to reveal the OS of the server in the HTTP headers - but this is thought unlikely).
BT 3.66m Netscape Enterprise Linux
Virgin Media 3.41m Apache Linux
AOL UK 1.53m AOLServer Unknown
Tiscali 1.48m Apache FreeBSD
Orange 1.06m Apache Solaris
TalkTalk 0.73m Apache Unknown
Pipex 0.57m Apache Solaris
Sky 0.55m IBM_HTTP_SERVER Unknown
Kingston 0.14m Microsoft-IIS Windows Server 2003
Thus 0.12m Apache Linux
This is consistent with Microsoft's traditional dominance of the small business space, where you would expect their market share to be growing as more and more small businesses come onto the web.
The big boys certainly aren't trusting their software - which is not surprising given that UNIX based implementations are tried and trusted for carrier grade implementations on the Internet.
Also unsurprisingly, the eminently configurable and reliable Apache web server still dominates.